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AIRPLANES, AIRSHIPS, 
AIRCRAFT ENGINES 



Airplanes, Airships, 
Aircraft Engines 



BY 



Lieut. ALBERT TUCKER, (CC) 
U.S.N. 



ANNAPOLIS, MARYLAND 

The United States Naval Institute 

1921 



it*?? 



Copyright, 1921 

BY 

UAS. W. CONROY 

Trustee for 

U. S. Naval Institute 

Annapolis, Md. 



a/r /M 



HOU 12'2I 

©CI.A630239 L 



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COMPOSED AND PRINTED AT THE 

WAVERLY PRESS 

By the Williams & Wilkins Company 

Baltimobe, Md., U. S. A. 



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FOREWORD 

This book has been prepared with the idea in view of 
furnishing a good practical knowledge of aircraft to the Naval 
Service. The nomenclature contained herein was compiled 
by the National Advisory Committee on Aeronautics, which 
is without question the best authority on the subject in 
this country. The writer is indebted to the above committee 
for the courtesy extended him in authorizing its publication 
in this book. The writer is also indebted to Lieutenant J. 
W. Iseman, U.S.N.R.F., and Ensign J. C. Eames, U.S.N. 
R.F., for valuable assistance rendered in preparation of data 
on instruments and aircraft engines. 

Lieutenant Albert Tucker, (CC), U.S.N. 

NOTE 

General Order No. 57, dated July 2, 1921, signed by the 
Secretary of the Navy, states that "Report No. 91 of the 
National Advisory Committee, entitled 'Nomenclature for 
Aeronautics' has been adopted as the official nomenclature for 
Aeronautics for use of the Army and Navy Air Services." 

This nomenclature is contained in this book. 

A. TUCKER. 



TABLE OF CONTENTS 

CHAPTER PAGES 

I. Nomenclature for aeronautics, alphabetically.. 11-52 
II. Explanations and definitions of various other 

terms used in connection with aircraft, etc. . 53-59 

III. Description of heavier-than-air craft and their 

construction in general 60-66 

IV. Woods used in the construction of aircraft, 

their defects, method of dry kilning, etc 67-87 

V. Propeller manufacture, splices, struts, wood 

protective coatings, etc 88-92 

VI. Aircraft wires, table of strengths, method of 

splicing, and their uses 93-104 

VII. Turnbuckles, shackles, clevis pins, etc 105-107 

VIII. Aircraft fittings, manufacture, welding, braz- 
ing, etc 108-120 

IX. Sand blasting and pickling 121-123 

X. Steel and copper tubes, brazing material 124-125 

XI. Enameling and painting metal parts 126-128 

XII. Fabrics, kinds, strengths and their application. 129-138 

XIII. Material used in the construction of H-16's and 

other flying boats 139-142 

XIV. Glues used in aircraft construction 143-144 

XV. Dopes and solvents 145-146 

XVI. Aircraft paints and insignia 147-154 

XVII. Aluminum and its alloys 155-157 

XVIII. Properties and use of duralumin 158-163 

XIX. Overhaul and alignment of aircraft 164-171 

XX. Checking alignment of seaplanes on beach, 

inspection of seaplanes after flight 172-175 

XXI. Care and preservation of aircraft and para- 
chutes in storage 176-177 

XXII. Aircraft dont's 178-184 

XXIII. The air speed meter, its functions, installation 

and troubles, calibration, etc 185-191 

XXIV. The altimeter, description, principles involved, 

troubles, etc 192-196 

7 



CONTENTS 



XXV. The recording barograph, description, troubles, 

corrections, etc 197-200 

XXVI. The tachometer, or revolution counter, descrip- 
tion, troubles, corrections, etc 201-205 

XXVII. The aero compass, description, compensation, 

etc 206-208 

XXVIII. The temperature gauge, description, calibra- 
tion, etc 209-211 

XXIX. The pressure gauge, description, etc 212 

XXX. The side slip indicator, description, etc 213-214 

XXXI. The fore and aft level, description, etc 215 

XXXII. The gyro turn indicator, description, etc 216-217 

XXXIII. Hydrogen leak detector, description, etc 218-219 

XXXIV. The manometer, description, etc 220 

XXXV. The statoscope, description, etc 221-222 

XXXVI. Balloons, manufacture of gases, Edwards effu- 
sion meter, its uses, etc., comalongand its uses 223-232 

XXXVII. Transportation of gas, etc 233-234 

XXXVIII. Interior inspection of balloons and airships, 
repairs, etc., dopes, gammeter valve, and mis- 
cellaneous questions and answers 235-251 

XXXL£. Method of folding free balloons, kite balloons 

and airships for storage 252-253 

XL. Inspection of balloons, rigging, and miscel- 
laneous questions 254-278 

XLI. Instructions for putting in service, rigging of 
cable and operating N. C. L. kite balloon 

winch. 279-285 

XLII. Balloons — fundamentals of operation, equip- 
ment, etc 286-297 

XLIII. Dilatable or expanding gore balloons 298-300 

XLIV. Formula aerostatics 301-303 

XLV. Method of preventing tail droop in envelope of 

airships 304 

XLVI. Airship mooring 305-309 

XLVII. Lighter-than-air-aircraft don't's 310-312 

XLVIII. Things to remember about airships 313-315 

XLIX. Aircraft engines — preliminary units and defi- 
nitions 316-337 

L. Aircraft ignition devices 338-343 

LI. Storage batteries 344-353 



CONTENTS 9 

LIL Magnetos 354-356 

LIII. Gasoline carburetion and carburetors 357-378 

LIV. Aircraft engine troubles 379-387 

LV. The Liberty aircraft engine : . . . 388-410 

LVI. Hispano-Suiza engine 411-416 

LVIL Inspection of Aircraft engines by aircraft engine 

mechanics 417-419 

LVIII. Lubricating oils, their manufacture and test, 

etc 420-426 

LIX. Reclamation of used oil 427^29 

Index 431-436 



CHAPTER I 

Nomenclature for Aeronautics Alphabetically 

Aerodynamic pitch. — (See Pitch.) 

Aerofoil. — A winglike structure; flat or curved, designed to 
obtain reaction upon its surfaces from the air through 
which it moves. 

Aerofoil section. — A section of an aerofoil made by a plane 
parallel to the plane of symmetry of the aerofoil and to 
the normal direction of motion. 

Aeronaut. — The pilot of an aerostat. 

Aerostat. — An aircraft which embodies a container filled 
with a gas lighter than air and which is sustained by 
the buoyancy of this gas; e.g., airship, balloon. 

Aerostatics. — The science which relates to the buoyancy and 
behavior of light er-than-air craft. 

Aerostation. — The operation of balloons and airships. Cor- 
responds to aviation, but refers to lighter-than-air craft. 

Aileron. — A hinged or pivoted movable auxiliary surface of 
an airplane, usually part of the trailing edge of a wing, 
the primary function of which is to impress a rolling 
moment on the airplane. (Fig. 1.) 

Air scoop. — A projecting cowl, which, by using the dynamic 
pressure of the relative wind or slip-stream, serves to 
maintain air pressure in the interior of the ballonet of 
an aerostat. (Fig. 2.) 

Aircraft. — Any form of craft designed for the navigation of 
the an* — airplanes, airships, balloons, helicopters, kites, 
kite balloons, ornithopters, gliders, etc. 

Airdome. — A field providing facilities for aircraft to land and 
take off and equipped with hangars, shops, and a supply 
depot for the storage, maintenance, and repair of air- 
craft. 11 



12 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Aileron- 




FIG. t. 




f «<5 2 



Tail j5ocw 




FlS.3 



NOMENCLATURE FOR AERONAUTICS 13 

Airplane. — A form of aircraft heavier than air which obtains 
support by the dynamic reaction of the air against the 
wings and which is driven through the air by a screw 
propeller. This term is commonly used in a more re- 
stricted sense to refer to airplanes fitted with landing- 
gear suited to operation from the land. If the landing 
gear is suited to operation from the water, the term 
seaplane ' ' is used . (See defi ni tion . ) 
Pusher. — A term commonly applied to a single engine 
airplane with the propeller in the rear of the main sup- 
porting surfaces. (Fig. 3.) 
Tandem. — An airplane with two or more sets of wings of 
substantially the same area (not including the tail 
unit) placed one in front of the other and on about the 
same level. 
Tractor. — A term commonly applied to a single engined 
airplane with the propeller forward of the main support- 
ing surfaces. (Fig. 4.) 
Airship. — A form of aerostat provided with a propelling sys- 
tem and with means of controlling the direction of move- 
ment. 
Nonrigid. — An airship whose form is maintained by the 

pressure of the contained gas. 
Rigid. — An airship whose form is maintained by a rigid 

structure contained within the envelope. 
Semirigid. — An airship whose form is maintained by means 
of a rigid or jointed keel and by gas pressure. 
Air speed. — (See Speed.) 
Air-speed indicator. — (See Indicator.) 
Altimeter. — An aneroid barometer, mounted on an aircraft, 

whose dial is marked in feet, yards, or meters. 
Anemometer. — Any instrument for measuring the velocity 

or force of the wind. 
Angle, critical. — The angle of attack at which the flow about 



14 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 




f&ACTOZ NOrfOPLAt<£. 
FIG. 4 




fyppe^cftx 



F»<3 6 



NOMENCLATURE FOR AERONAUTICS 15 

an aerofoil changes abruptly, with corresponding abrupt 
changes in the lift and drag coefficients. An aerofoil 
may have two or more critical angles, one of which al- 
most always corresponds to the angle of maximum lift. 

Angle, dihedral. — The main supporting surfaces of an air- 
plane are said to have a dihedral angle when both right 
and left wings are upwardly or downwardly inclined to a 
horizontal transverse line. The angle is measured by the 
inclination of each wing to the horizontal. If the in- 
clination is upward, the angle is said to be positive; if 
downward, negative. The several main supporting 
surfaces of an airplane may have different amounts of 
dihedral. (Fig. 5.) 

Angle, downwash. — The acute angle through which the air 
stream relative to the airplane is deflected by an aero- 
foil. It is measured in a plane parallel to the plane of 
symmetry. 

Angle, gliding. — The acute angle which the flight path makes 
with the horizontal when descending in still air under 
the influence of gravity alone; i.e., without power from 
the engine. 

Angle, landing. — The angle of attack of the main supporting 
surfaces of an airplane at the instant of touching the 
ground in a three point landing; i.e., the angle between 
the wing chord and the horizontal when the machine is 
resting on the ground in its normal position. 

Angle of attack. — The acute angle between the direction of 
the relative wind and the chord of an aerofoil; i.e., the 
angle between the chord of an aerofoil and its motion 
relative to the air. (This definition may be extended 
to any body having an axis.) 

Angle of incidence (in directions for rigging). — In the proc- 
ess of rigging an airplane some arbitrary definite line 
in the airplane is kept horizontal; the angle of incidence 



16 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

of a wing, or of any aerofoil, is the angle between its 
chord and this horizontal line, which may be the line of 
the upper longerons of the fuselage or nacelle or the 
thrust line. 

Angle of pitch. — The angle between two planes denned as 
follows: One plane includes the lateral axis of the air- 
craft and the direction of the relative wind; the other 
plane includes the lateral axis and the longitudinal axis. 
(In normal flight the angle of pitch is, then, the angle 
between the longitudinal axis and the direction of the 
relative wind.) This angle is positive when the nose of 
the aircraft rises. 

Angle of propeller blade setting. — The angle which the 
chord of a propeller section makes with a plane perpen- 
dicular to the axis of the propeller. This angle varies 
along the blade, increasing as the boss is approached. 

Angle of roll, or angle of bank. — The angle through which 
an aircraft must be rotated about its longitudinal axis 
in order to bring its lateral axis into a horizontal plane. 

Angle of tail setting. — The acute angle between the chord 
of the wings of an airplane and the chord of the tail 
plane. 

Angle of yaw. — The angle between the direction of the rela- 
tive wind and the plane of symmetry of an aircraft. 
This angle is positive when the aircraft turns to the right. 

Angle of zero lift. — (See Zero lift angle.) 

Antidrag wires. — (See Wires.) 

Antilift wires. — (See Wires.) 

Apparent pressure. — The excess of pressure inside the en- 
velope of an aerostat over the atmospheric pressure. In 
the case of an airship, the excess of pressure is measured 
at the bottom of the envelope unless otherwise specified. 

Appendix. — The tube at the bottom of a balloon, used for in- 
flation. In the case of a spherical balloon it also serves 



NOMENCLATURE FOR AERONAUTICS 17 

to increase the "head" of gas, and so to build up an in- 
ternal pressure sufficient to keep the envelope from being 
pulled out of shape by the weight of the basket. (Fig. 6.) 

Aspect ratio. — The ratio of span to mean chord of an aerofoil. 

Aspect ratio of propeller. — The ratio of propeller diameter to 
maximum blade width. 

Attack, angle of. — (See Angle.) 

Attitude. — The attitude of an aircraft is determined by the 
inclination of its axes to a "frame of reference" fixed to 
the earth, i.e., the attitude depends entirely on the posi- 
tion of the aircraft as seen by an observer on the ground. 

Automatic valve.— An automatic escape and safety valve for 
the purpose of regulating internal pressure in an aero- 
stat. 

Aviator. — The operator or pilot of heavier-than-air craft. 
This term is applied regardless of the sex of the operator. 

Axes of an aircraft. — Three fixed lines of reference; usually 
centroidal and mutually rectangular. (Fig. 7.) 

The principal longitudinal axis in the plane of sym- 
metiy, usually parallel to the axis of the propeller, is 
called the longitudinal axis; the axis perpendicular to 
this in the plane of symmetry is called the normal axis; 
and the third axis, perpendicular to the other two, is 
called the lateral axis. In mathematical discussions the 
first of these axes, drawn from front to rear, is called the 
X axis; the second, drawn upward, the Z axis; and the 
third, running from right to left, the Y axis. 

Balanced surface. — (See Surface.) 

Ballonet. — A small balloon within the interior of a balloon or 
airship for the purpose of controlling the ascent or de- 
scent and for maintaining pressure on the outer envelope 
so as to prevent deformation. 

Balloon. — A form of aerostat deriving its support in the air 
from the buoyancy of the air displaced by an envelope, 



18 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

the form of which is maintained by the pressure of a 
contained gas lighter than air, and having no power 
plant or means of controlling the direction of flight in 
the horizontal plane. 

Barrage. — A small captive balloon, raised as a protection 
against attacks by airplanes. 

Captive. — A balloon restrained from free flight by means 
of a cable attaching it to the earth. 

Kite. — An elongated form of captive balloon, fitted with 
tail appendages to keep it headed into the wind, and 
usually deriving increased lift due to its axis being incli- 
ned to the wind. A Caquot balloon is of this type. 
(Fig. 8.) 

Nurse. — A small balloon made of heavy fabric, employed 
as a portable means for storing gas. Sometimes one is 
so connected as to automatically allow for the expansion 
or contraction of the gas in an aerostat when on the 
ground. 

Pilot. — A small balloon sent up to show the direction of 
the wind by observations of its flight with theodolites. 

Sounding. — A small balloon sent aloft without passengers 
but with registering meteorological and other instru- 
ments. 
Balloon bed. — A mooring place on the ground for a captive 

balloon. 
Balloon fabric. — (See Fabric.) 

Bank. — To incline an airplane laterally. Right bank is to 
incline the airplane with the right wing down. Also 
used as a noun to describe the position of an airplane 
when its lateral axis is inclined to the horizontal. 
Bank, angle of. — (See Angle of roll.) 

Barograph. — An instrument used to make a permanent 
record of variations in barometric pressure. In aero- 
nautics the charts on which the records are made some- 



NOMENCLATURE FOR AERONAUTICS 



19 




A*es of an, A/rop/or*e, 
FIG. 7- 




20 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

times indicate altitudes directly instead of barometric 
pressure. 

Barrage balloon. — (See Balloon.) . 

Barrel roll. — An aerial maneuver in which a complete revolu- 
tion about the longitudinal axis is made, the direction 
of flight being approximately maintained. 

Basket. — The car suspended beneath a balloon for pas- 
sengers, ballast, etc. 

Bay. — The cubic section of a truss included between two 
transversely adjacent sets of struts of an airplane. The 
first bay is the one closest to the plane of symmetry. 

Biplane. — A form of airplane whose main supporting surface 
is divided into two parts, superimposed. 

Blade back. — The markedly convex surface of a propeller 
blade which corresponds to the upper surface of an aero- 
foil. 

Blade face. — The surface of a propeller blade, flat or slightly 
cambered near the tips, which corresponds to the lower 
surface of an aerofoil. 

Blade setting, angle of. — (See Angle.) 

Blade width ratio. — The ratio of the width of a propeller 
blade at any point to the circumference of the circle 
along which that point travels when the propeller is 
rotating and the airplane is held stationary. When 
used without qualifying terms, it refers to the ratio of 
the maximum blade width to the circumference of the 
circle swept by the propeller. 

Boat seaplane. — (See Seaplane.) 

Bonnet. — The appliance, having the form of a parasol, which 
protects the valve of a spherical balloon against rain. 

Boss. — The central portion of an airscrew. The portion in 
which the hub is mounted. 

Bow stiffeners. — Rigid members attached to the bow of a 
nonrigid or semirigid envelope to reinforce it against the 



NOMENCLATURE FOR AERONAUTICS 21 

pressure caused by the motion of the airship. (Some- 
times called nose stiff eners.) 

Bridle. — A sling of cordage which has its ends attached to 
the envelope of a balloon or airship and a rope or cable 
running from an intermediate point. 

Bulkhead. — A transverse structural member of a fuselage or 
nacelle, continuous around the periphery. 

Buoyancy. — The upward force exerted on a lighter-than-air 
craft due to the air which it displaces. 
Center of. — The center of volume of the gas container or 
the center of gravity of the gas (envelope) of a balloon 
or airship. 
Gross. — The total upward force on an aerostat at rest; the 
total volume multiplied by the difference of density of 
the air and the contained gas. 
Positive and negative. — The positive or negative difference 
between the buoyancy and the weight of a balloon or 
airship. The unbalanced force which causes ascent or 
descent. 

Cabane. — A pyramidal or prismoidal framework to which 
wire or cable stays are secured. 

Camber. — The convexity or rise of the curve of an aerofoil 
from its chord, usually expressed as the ratio of the max- 
imum departure of the curve from the chord to the length 
of the chord. "Top camber" refers to the top surface of 
an aerofoil and "bottom camber" to the bottom surface; 
"mean camber" to the mean of these two. 

Camber ratio. — The ratio of the maximum ordinate of a pro- 
peller section is its chord. 

Capacity. — The cubic contents or volume of an aerostat. 

Captive balloon. — (See Balloon.) 

Caquot balloon. — (See Balloon, kite.) 

Car. — The nacelle of an airship. 



22 AIRPLANES, AIRSHIPS, AIRCKAFT ENGINES 

Ceiling: 
Absolute. — The maximum height above sea level which a 
given aircraft can approach asymptotically, assuming 
standard air conditions. 
Service. — The height above sea level at which a given air- 
craft ceases to rise at a rate higher than a small specified 
one (100 feet per minute in United States Air Service). 
This specified rate may be different in the services of 
different countries. 

Cell. — The entire structure of the wings and wing trussing 
on one side of the fuselage of an airplane, or between 
fuselage or nacelles, where there are more than one. 

Center of pressure of an aerofoil section. — The point in the 
chord of an aerofoil section, prolonged if necessary, 
through which at any given attitude the line of action 
of the resultant air force passes. 

Chord: 

Of an aerofoil section. — The fine of a straightedge brought 
into contact with the lower surface of the section at two 
points. In the case of an aerofoil having double convex 
camber the straight line joining the leading and trailing 
edges. (These edges may be defined, for this purpose, 
as the two points in the section which are farthest apart. 
(Fig. 9.) 
Length. — The length of the projection of the aerofoil sec- 
tion on its chord. 

Chord, mean, of a wing. — The quotient obtained by dividing 
the wing area by the extreme dimension of the wing pro- 
jection at right angles to the chord. 

Climb, rate of. — The vertical component of the air speed of an 
aircraft; i.e., its vertical velocity with reference to the 
air. 

Cockpit. — The open spaces in which the pilot and passengers 
are accommodated. A cockpit is never completely 
housed in. 



NOMENCLATURE FOR AERONAUTICS 23 

Concentration ring: 
Airship. — A metal ring to which several rigging lines are 
brought from the envelope and from which one or more 
lines also lead to the car. 
Free balloon. — A hoop to which are attached the ropes 
suspending the basket and to which the net is also 
secured. 
Parachute. — A hoop to which the rigging of the parachute 
is attached and also the line sustaining the passenger. 

Consumption per B.H.P. hour. — The quantity of fuel or oil 
consumed per hour by an engine running at ground level 
divided by the brake horsepower developed, unless 
specifically stated otherwise. 

Control column or yoke. — A control lever with a rotatable 
wheel mounted at its upper end. (See Control stick.) 
Pitching is controlled by fore-and-aft movement of the 
column; rolling, by rotation of the wheel. " Wheel con- 
trol" is that type of control in which such a column or 
yoke is used. 

Control stick. — The vertical lever by means of which certain 
of the principal controls of an airplane are operated. 
Pitching is controlled by a fore-and-aft movement of 
the stick, rolling by side-to-side movement. "Stick 
control" is that type of control in which such a stick is 
used. 

Controls. — A general term applying to the means provided to 
enable the pilot to control the speed, direction of flight, 
attitude, and power of an aircraft. 

Cord. — A species of wire made up of several strands (usually 
7) twisted together as in a rope, each of the strands, in 
turn, being made up of several (usually 19) individual 
wires. 

Cowling. — The metal covering which houses the engine and 
sometimes a portion of the fuselage or nacelle as well. 



24 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Critical angle. — (See Angle.) 

Cross-wind force. — The component perpendicular to the 
lift and to the drag of the total force on an aircraft due 
to the air through which it moves. 

Crow's-foot. — A system of diverging short ropes for dis- 
tributing the pull of a single rope. 

Damping factor. — The percentage of damping in one period. 

Dead load — (See Load.) 

Dihedral angle. — (See Angle.) 

Disk area. — The total area swept by a propeller, i.e., the 
area of a circle having a diameter equal to the propeller 
diameter. 

Dischargeable weight. — The excess of the gross buoyancy 
over the dead load, the crew and such items of equip- 
ment as are essential to enable an airship to fly and land 
safely. 

Dive. — A steep glide. 

Divergence. — A disturbance which increases without oscil- 
lation. 

Dope, airplane. — A general term applied to the material used 
in treating the cloth surface of airplane members to 
increase strength, produce tautness, and act as a filler 
to maintain airtightness. 

Downwash angle. — (See Angle.) 

Drag. — The component parallel to the relative wind of the 
total force on an aerofoil or aircraft due to the air through 
which it moves. 

In the case of an airplane, that part of the drag due 
to the wings is called "wing resistance;" that due to 
the rest of the airplane is called " structural" or " para- 
site resistance." 

Drag rope. — The rope dropped by an airship in order to 
allow it to be secured by a landing party. 



NOMENCLATURE FOR AERONAUTICS 25 

Drag strut. — A compression member of the internal bracing 
system of an aerofoil. 

Drag wires. — (See Wires.) 

Drift. — The angular deviation from a set course over the 
earth, due to cross currents of wind, hence, " drift meter." 

Drift meter. — An instrument for the measurement of the 
angular deviation of an aircraft from a set course, due 
to cross winds. 

Drip flap. — A strip of fabric attached by one edge to the 
envelope of an aerostat so that rain runs off its free 
edge instead of dripping into the basket or car. The 
drip flap assists also to keep the suspension ropes dry 
and nonconducting. 

Dry weight. — The weight of an engine, including carbu- 
retors, propeller-hub assembly, and ignition system 
complete, but excluding exhaust manifolds. 

Dynamic factor. — The ratio between the load carried by any 
part of an aircraft when accelerating or when otherwise 
subjected to abnormal conditions and the load carried 
in normal flight. 

Dynamic lift. — (See Lift.) 

Effective pitch.— (See Pitch.) 

Elevator. — A movable auxiliary surface of an airplane, us- 
ually attached to the tail plane, the function of which 
is to impress a pitching moment on the aircraft. (Fig. 
10.) 

Empennage. — Same as tail unit. 

Envelope. — The outer covering of a rigid airship; or, in the 
case of a balloon or a nonrigid airship, the bag which 
contains the gas. 

Equator. — The largest horizontal circle of a spherical balloon. 

Fabric, balloon. — The finished material, usually rubberized, 
of which balloon or airship envelopes are made. 



AIRPLANES, AIRSHIPS, AIRCBAFT ENGINES 



CkoTiet length.- 




P/anG^^^Cy- Rudder 
7%/L V/V/T 

' Pig. 10 




Pig- ii 



NOMENCLATURE FOR AERONAUTICS 27 

Biased. — Plied fabric in which the threads of the plies are 

at an angle to each other. 
Parallel. — Plied fabric in which the threads of the plies 
are parallel to each other. 

Factor, dynamic. — (See Dynamic factor.) 

Factor of safety. — The ratio of the ultimate strength of a 
member to the maximum possible load occurring under 
conditions specified. 

Fairing. — A member whose primary function is to produce a 
smooth outline and to reduce head resistance or drag. 

Fins. — Small stationary surfaces, substantially vertical, at- 
tached to different parts of aircraft, in order to promote 
stability; for example, tail fins, skid fins, etc. Fins are 
sometimes adjustable. (Fig. 10.) 
Skid fins. — Fore and aft vertical surfaces, usually placed 
well out toward the tips of the upper plane, designed to 
provide the vertical keel-surface required for stability. 

Fins, kite balloon. — The air inflated lobes intended to keep 
the balloon headed into the wind. 

Fire wall. — A metal plate, so set as to isolate from the engine 
the other parts of the airplane structure, and thus to 
reduce the risk from a backfire. 

Fitting. — A generic term for any small metal part used in 
the structure of an airplane. 

Flight path. — The path of the center of gravity of an air- 
craft with reference to the ear^h. 

Float. — A completely inclosed water-tight structure attached 
to an aircraft in order to furnish it buoyancy when in 
contact with the surface of the water. In float seaplanes 
the crew is carried in a fuselage or nacelle separate from 
the float. 

Floating seaplane. — (See Seaplane.) 

Flotation gear. — An emergency landing gear attached to an 
airplane, which will permit of safe landing on the water 



28 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

and provide buoyancy when resting on the surface of 
the water. 

Flying boat. — (See Seaplane.) 

Free-flight testing. — The conduct of special flight tests of 
a scientific nature, as contrasted with performance 
testing. 

Full load.— (See Load.) 

Fuselage. — The elongated structure, of approximately 
steamline form, to which are attached the wings and 
tail unit of an airplane. In general, it is designed to 
hold the passengers. 

Fuselage, length of. — The distance from the nose of the fuse- 
lage (including the engine bed and radiator, if present) 
to the after end of the fuselage, not including the con- 
trol and stabilizing surfaces. 

Gap. — The shortest distance between the planes of the chord 
of the upper and lower wings of a biplane, measured 
along a line perpendicular to the chord of the upper 
wing at any designated point of its entering edge. (Fig. 

no 

Geometrical pitch. — (See Pitch.) 

Glide, to. — To descend at a normal angle of attack without 
engine power sufficient for level flight, the propeller 
thrust being replaced by a component of gravity along 
the line of flight. 

Glider. — A form of aircraft similar to an airplane, but with- 
out any power plant. Gliders are used chiefly for sport. 

Gliding angle. — (See Angle.) 

Gore. — The portion of the envelope of a balloon or airship 
included between two adjacent meridian seams. 

Gross buoyancy. — (See Buoyancy.) 

Ground cloth. — Canvas placed on the ground to protect a 
balloon. 



NOMENCLATURE FOR AERONAUTICS 29 

Ground speed. — (See Speed.) 

Handling truck. — A truck, mounted on wheels or sliding on 
ways, on which airplanes or seaplanes may be placed 
to facilitate moving them about and carrying them to 
and from their hangars. 

Hangar. — A shelter for housing aircraft. 

Helicopter. — A form of aircraft whose support in the air is 
derived from the vertical thrust of propellers. 

Hog (Airship). — A distortion of the envelope in which the 
axis becomes convex upward or both ends droop. 

Horn. — The operating lever of a control sufrace of an air- 
craft, e.g., aileron horn, rudder horn, elevator horn. 

Horsepower of an engine, maximum. — The maximum horse- 
power which can be safely maintained for periods not 
less than five minutes. 

Horsepower of an engine, normal. — The highest horsepower 
which can be safely maintained for long periods. 

Hull (airship). — The main structure of a rigid airship, con- 
sisting of a covered elongated framework which incloses 
the gas bags and which supports the cars and equipment. 

Hull (seaplane). — The portion of a boat seaplane which fur- 
nishes buoj^ancy when in contact with the surface of 
the water, to which the main supporting surfaces and 
other parts are attached, and which contains accommo- 
dations for the crew. 

Incidence, angle of. — (See Angle.) 

Inclinometer : 

Absolute. — An instrument giving the attitude of an air- 
craft with reference to true gravity. 
Relative. — An instrument giving the attitude of an air- 
craft with reference to apparent gravity. Such in- 
struments are sometimes incorrectly referred to as 
banking indicators. 

Indicator, air-speed. — An anemometer mounted on an air- 



30 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 






craft for the purpose of indicating the speed of the air- 
craft. 
True air-speed indicator. — An instrument, usually work- 
ing on the principle of the Biram or Robinson ane- 
mometers, which gives the true air speed, independent 
of density. 
Apparent air-speed indicator. — An instrument, usually de- 
pendent on pressure measurements, the readings of which 
vary with the density of the air. 

Indraft. — The drawing in of air from in front of a propeller 
by the action of the rotating blades. The indraft ve- 
locity relative to the propeller is somewhat higher than 
that of the undisturbed air at most points of the propeller 
disk. 

Inspection window. — A small transparent window in the 
envelope of a balloon or in the wing of an airplane to 
allow inspection of the interior. 

Jackstay. — A longitudinal rigging provided to maintain the 
correct distance between the heads of various riggings 
on an airship. 

Keel. — A member or assembly of members which provides 
longitudinal strength to an airship of rigid or semirigid 
type. In the case of a rigid airship the keel is usually 
an elaborately trussed girder and may be inclosed with- 
in the envelope or may project beyond (usually below) 
the regular cross-sectional form of the envelope. 
Articulated. — A keel made up of a series of members 
hinged together at their ends. 

King post. — The main compression member of a trussing 
system applied to a member subject to bending. 
(Fig. 4.) 

Kite. — A form of aircraft without other propelling means 
than the towline pull, whose support is derived from 
the force of the wind moving past its surface. 



NOMENCLATURE FOR AERONAUTICS 31 

Kite balloon. — (See Balloon.) 

Laminated wood. — Wooden parts made up by gluing or 

otherwise fastening together individual wood planks or 
laminations with the grain substantially parallel. 

Landing angle. — (See Angle.) 

Landing field. — A field of such a nature as to permit of air- 
planes landing or taking off. 

Landing gear. — The understructure of an aircraft designed 
to carry the load when in contact with the land or water. 

Leading edge. — The foremost edge of an aerofoil or propeller 
blade. 

Length, chord. — (See Chord.) 

Length, fuselage. — (See Fuselage.) 

Length, over-all. — (See Over-all.) 

Lift. — The component of the total air force which is perpen- 
dicular to the relative wind and in the plane of sym- 
metry. It must be specified whether this applies to a 
complete aircraft or parts thereof. (In the case of an 
airship this is often called "dynamic lift.") 

Lift wires. — (See Wires.) 

Load : 
Dead. — The structure, power plant, and essential acces- 
sories of an aircraft. Included in this are the water in 
the radiator, tachometer, thermometer, gauges, air- 
speed indicators, levels, altimeter, compass, watch and 
hand starter, and also, in the case of an aerostat, the 
amount of ballast which must be carried to assist in 
making a safe landing. 
Full. — The total weight of an aircraft when loaded to the 
maximum authorized loading of that particular type. 
Useful. — The excess of the full load over the dead load 
of the aircraft itself. Therefore useful load includes 
the crew and passengers, oil and fuel, ballast, electric- 
light installation, chart board, detachable gun mounts, 
bomb storage and releasing gear, wireless apparatus, etc. 



32 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Load factor. — The ratio of the ultimate strength of a member 
to the load under horizontal steady rectilinear flight 
conditions. 

Lobes. — Inflated bags at the stern of an elongated balloon, 
designed to give it directional stability. Also used to 
denote the sections into which the envelope is some- 
times (e.g., in the Astra-Torres) divided by the tension 
of the internal rigging. 

Longeron. — A fore-and-aft member of the framing of an air- 
plane fuselage or nacelle, usually continuous across a 
number of points of support. (Fig. 12.) 

Loop. — An aerial maneuver in which the airplane describes 
an approximately circular path in the plane of the longi- 
tudinal and normal axes, the lateral axis remaining hori- 
zontal, and the upper side of the airplane remaining on 
the inside of the circle. 

Main supporting surface. — (See Surface.) 

Margin of power. — (See Power.) 

Mean chord of a wing. — (See Chord.) 

Mean chord of a combination of wings. — (See Chord.) 

Mean span. — (See Span, mean.) 

Minimum speed. — (See Speed.) 

Monocoque. — A type of fuselage which is constructed by 
wrapping strips of veneer around formers, and in which 
the veneer is primarily depended on to carry stresses 
arising in the fuselage. 

Monoplane. — A form of airplane which has but one main 
supporting surface extending equally on each side of the 
body. 

Mooring harness. — The system of bands of tape over the top 
of a balloon to which are attached the mooring ropes. 

Multiplane. — A form of airplane whose main supporting sur- 
face is divided into four parts, superimposed. 



NOMENCLATURE FOR AERONAUTICS 33 

Nacelle. — The inclosed shelter for passengers or for a power 
plant. A nacelle is usually shorter than a fuselage, and 
does not carry the tail unit. 

Net. — A rigging made of ropes and twine on spherical bal- 
loons which supports the weight of the basket, etc., 
distributing the load over the entire upper surface of 
the envelope. 

Nonrigid airship. — (See Airship.) 

Nose cap. — A cap used to reinforce the bow stiffeners of an 
airship. 

Nose heavy. — The condition of an aircraft in which, in any 
given condition of normal flight, the nose tends to drop 
if the longitudinal control is released; i.e., the condition 
in which the pilot has to exert a pull on the control 
stick or column to maintain the given condition. 

Nurse balloon. — (See Balloon.) 

Ornithopter. — A form of aircraft deriving its support and 
propelling force from flapping wings. 

Oscillation, phugoid. — A long period oscillation characteristic 
of the disturbed longitudinal motion of an airplane. 

Oscillation, stable. — An oscillation which tends to die out. 

Oscillation unstable. — An oscillation of which the amplitude 
tends to increase. 

Over-all length. — The distance from the extreme front to 
the extreme rear of an aircraft, including the propeller 
and the tail unit. 

Overhang. — One-half the difference in the span of any two 
main supporting surfaces of an airplane. The over- 
hang is positive when the upper of the two main sup- 
porting surfaces has the larger span. (Fig. 5.) 

Pancake, to. — To il level off" an airplane higher than for a 
normal landing, causing it to stall and descend with the 
wings at a very large angle of attack and approximately 
without bank, on a steeply inclined path. 



34 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Panel aerostat. — The unit piece of fabric of which the enve- 
lope of an aerostat is made. 

Panel airplane. — A portion of a wing of an airplane which is 
constructed entirely separately from the rest of the 
wing, and which is attached to the remainder by bolts 
and fittings. 

Parachute. — An apparatus used to retard the descent of a 
falling body by offering resistance to motion through 
the air; usually made of light fabric with no rigid parts. 

Parasite resistance. — (See Drag.) 

Patch, airship. — A strengthened or reinforced flap of fabric, 
of variable form according to the maker, which is 
cemented to the envelope and forms an anchor by which 
some portion of the machine is attached to the envelope. 
(Fig. 2.) 

Performance. — The maximum and minimum speeds and 
rate of climb at various altitudes, the time to climb to 
these altitudes, and the ceiling constitute the perform- 
ance characteristic of an airplane. 

Performance testing. — The process of determining the 
performance characteristics of an airplane. 

Period. — The time taken for a complete oscillation. 

Permeability. — The measure of the rate of diffusion of gas 
through intact balloon fabric; usually expressed in cubic 
meters per square meter per 24 hours. 

Phillips' entry. — A reversal of curvature of the lower surface 
of an aerofoil near the leading edge. The result is to 
decrease the drag and provide more depth for the front 
spar. (Fig. 9.) 

Phugoid oscillation. — (See Oscillation.) 

Pilot balloon. — (See Balloon.) 

Pitch of propeller: 

Pitch, aerodynamic. — The distance a propeller would 
have to advance in one revolution in order that the 
torque might be zero. 



r NOMENCLATURE FOR AERONAUTICS 35 

Pitch, effective. — The distance an aircraft advances along 

its flight path for one revolution of the propeller. 
Pitch, geometrical. — The distance an element of a pro- 
peller would advance in one revolution if it were turning 
in a solid nut; i.e., if it were moving along a helix of 
slope equal to the angle between the chord of the element 
and a plane perpendicular to the propeller axis. The 
mean geometrical pitch of a propeller, which is a quantity 
commonly used in specifications, is the mean of the 
geometrical pitches of the several elements. 

Pitch, standard. — The "pitch of a propeller" is usually 
stated as the geometrical pitch taken at two-thirds of 
the radius. 

Pitch, virtual. — The distance a propeller would have to 
advance in one revolution in order that there might 
be no thrust. 

Pitch, angle of. — (See Angle.) 

Pitch slip.— (See Slip.) 

Pitch speed. — (See Speed.) 

Pitot tube. — A tube with an end open square to a fluid 
stream. It is exposed with the open end pointing 
upstream to detect an impact pressure. It is usually 
associated with a coaxial tube surrounding it, having 
perforations normal to the axis for indicating static 
pressure; or there is such a tube placed near it and 
parallel to it, with a closed conical end and having 
perforations in its side. The velocity of the fluid can 
be determined from the difference between the impact 
pressure and the static pressure, as read by a suitable 
gauge. This instrument is often used to determine the 
velocity of an aircraft through the air. (Fig. 13.) 

Plywood. — A product formed by gluing together two or more 
layers of wood veneer. 



36 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Power, margin of. — The difference between the power avail- 
able at any given speed and in air of given density and 
the power required for level flight under the same 
conditions. The best rate of climb at any altitude 
depends on the maximum margin of power. 

Power loading. — The weight per horsepower, computed on 
a basis of full load and of power in air of standard 
density unless otherwise stated. 

Pressure nozzle. — The apparatus which, in combination 
with a gauge, is used to measure the pressure due to 
speed through the air. Includes both Pitot and Venturi 
tubes. Pressure nozzles of various types are also used 
in yawmeters and other instruments. 

Proofing. — Material applied to the fabric of an aerostat at 
the time of manufacture to protect it against weather 
or to prevent the passage of gas. 

Propeller, pusher. — A propeller which is placed at the rear 
end of its shaft and pushes against the thrust bearing. 

Propeller, tractor. — A propeller which is placed at the for- 
ward end of its shaft and pulls on the thrust bearing. 

Purity of a gas. — The percentage, by number of molecules, 
of the light gas used for inflation, such as hydrogen, to 
all the gases within the container. 

Pusher airplane. — (See Airplane.) 

Pusher propeller. — (See Propeller.) 

Quadruplane. — A form of airplane whose main supporting 
surface is divided into four parts, superimposed. 

Race rotation. — The rotation of the air influenced by a 
propeller. This rotation is much more marked in the 
slip stream than in front of the propeller. 

Rake. — The cutting away of the wing tip at an angle so that 
the main supporting sufraces seen from above will 
appear of trapezoidal form. The amount of rake is 
measured by the angle between the straight portion of 



NOMENCLATURE FOR AERONAUTICS 37 

the wing-tip outline and the plane of symmetry. The 
rake is positive when the trailing edge is longer than 
the leading edge. 

Rake, blade. — The angle which the line joining the centroids 
of the sections of a propeller blade makes with a plane 
perpendicular to the propeller shaft. The rake is 
positive when the blades are thrown forward. 

Rate of climb. — The vertical component of the air speed of 
an aircraft; i.e., its vertical velocity with reference to 
the air. 

Rate-of-climb indicator. — An instrument indicating the 
vertical component of the velocity of an aircraft. Most 
rate-of-climb meters depend on the rate of change of 
the atmospheric pressure. 

Relative wind. — The motion of the air with reference to a 
moving body. Its direction and velocity, therefore, are 
found by adding two vectors, one being the velocity of 
the air with reference to the earth, the other being equal 
and opposite to the velocity of the body with reference 
to the earth. 

Resistance derivatives. — Quantities expressing the variation 
of the forces and moments on aircraft due to disturbance 
of steady motion. They form the experimental basis 
of the theory of stability, and from them the periods 
and damping factors of aircraft can be calculated. In 
the general case there are 18 translatory and 18 rotary 
derivatives. 

Rotary. — Resistance derivatives expressing the variation of 
moments and forces due to small increases in the rota- 
tional velocities of the aircraft. 

Translatory. — Resistance derivatives expressing the varia- 
tion of moments and forces due to small increases in the 
translatory velocities of the aircraft. 



38 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Reverse turn. — A rapid maneuver to reverse the direction 
of flight of an airplane, made by a half loop and half roll 
in either sequence. 

Revolutions, maximum. — The maximum number of revolu- 
tions per minute that may be maintained for periods 
not less than 5 minutes. 

Revolutions, normal. — The highest number of revolutions 
per minute that may be maintained for long periods. 

Rib.— (See Wing rib.) 

Rigger. — One who is employed in assembling and aligning 
aircraft. 

Rigging. — The assembling and aligning of an aircraft. 

Right-hand engine. — An engine the final power delivery shaft 
of which rotates clockwise when viewed by an observer 
looking along the engine toward the power delivery end. 

Righting moment. — A moment which tends to restore an 
aircraft to its previous attitude after any small rotational 
displacement. 

Rigid airship. — (See Airship.) 

Rip cord. — The rope running from the rip panel of a balloon 
or nonrigid airship to the basket, the pulling of which 
tears off the rip panel and causes immediate deflation. 

Rip panel. — A strip in the upper part of a balloon or nonrigid 
airship which is torn off when immediate deflation is 
desired. 

Roll, angle of. — (See Angle.) 

Rudder. — A hinged or pivoted surface used for the purpose 
of impressing yawing moments on an aircraft; i.e., for 
controlling its direction of flight. (Fig. 10.) 

Rudder bar. — The foot bar by means of which the rudder is 
operated. 

Rudder torque. — The twisting effect exerted by the rudder 
on the fuselage, due to the relative displacement of the 
center of pressure of the rudder. The product of the 



NOMENCLATUEE FOR AERONAUTICS 39 

rudder area by the distance from its center of area to 
the center line of the fuselage may be used as a relative 
measure of rudder torque. 

Safety, factor of. — (See Factor of Safety.) 

Safety loop. — A loop formed immediately outside the conical 
reversing bag through which the valve rope emerges 
from the bottom of an aerostat. Before the automatic 
valve can be opened by the aid of the valve rope the 
fastening of the safety loop is torn off by a strong pull 
on the valve rope from the nacelle. 

Seaplane. — A particular form of airplane designed to rise 
from and land on the water. 
Boat seaplane, or flying boat. — A form of seaplane having 
for its central portion a boat which provides notation. 
It is often provided with auxiliary floats or pontoons. 
(Fig. 14.) 
Float seaplane. — A form of seaplane in which the landing 

^gear consists of one or more floats or pontoons (Fig. 
15.) 

Semirigid airship. — (See Airship.) 

Serpent. — A short, heavy trail rope. 

Shock absorber. — A spring or elastic member, designed to 
prevent the imposition of large accelerations on the 
fuselage, wings, and other heavy concentrated weights. 
Shock absorbers are usually interposed between the 
wheels, floats, or tail skid, and the remainder of the 
airplane to secure resiliency in landing and taxi-ing. 

Shock-absorber hysteresis. — The ratio of the work absorbed 
in the shock absorber during one complete cycle to the 

k total energy transmitted to the shock absorber during 
the first half of the cycle, 
hutters. — The adjustable blinds or vanes which are used to 
control the amount of air flowing through the radiator 
and so to regulate the temperature of the cooling water. 



40 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



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Static pressure. 




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NOMENCLATURE FOR AERONAUTICS 41 

Side slipping. — Sliding with a component of velocity along 
the lateral axis which is inclined and in the direction of 
the lower end of that axis. When it occurs in connection 
with a turn it is the opposite of skidding. 

Skid fins.— (See Fins.) 

Skidding. — Sliding sidewise away from the center of curva- 
ture when turning. It is usually caused by banking 
insufficiently and is the opposite of side slipping. 

Skids. — Runners used as members of the landing gear and 
designed to aid the aircraft in landing or taxi-ing. 
Tail skid. — A skid used to support the tail when in contact 

with the ground. 
Wing skid. — A skid placed near the wing- tip and designed 
to protect the wing from contact with the ground. 

Skin friction. — The tangential component of the fluid force 
at a point on a surface. It depends on the viscosity 
and density of the fluid, the total surface area and the 
roughness of the surface of the object. 

Slip. — The difference between the effective pitch and the 
mean geometrical pitch. Slip is usually expressed as a 
percentage of the mean geometrical pitch. 

Slip stream. — The stream of air behind a propeller. 

Soar, to. — To fly without engine power and without loss of 
altitude. Lightly loaded gliders will soar in rising 
currents of air. 

Sounding balloon. — (See Balloon.) 

Span, or spread. — The maximum distance laterally from tip 
to tip of an airplane inclusive of ailerons, or the lateral 
dimension of an aerofoil. 

Speed: 
Air. — The speed of an aircraft relative to the air. 
Ground. — The horizontal component of the velocity of an 
aircraft relative to the earth. 



42 .■ AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Speed, minimum. — The lowest speed which can be main- 
tained in level flight, with any throttle setting whatever. 

Speed, pitch. — The product of the mean geometrical pitch 
by the number of revolutions of the propeller in unit 
time; i.e., the speed the aircraft would make if there 
were no slip. 

Spin. — An aerial maneuver consisting of a combination of 
roll and yaw, with the longitudinal axis of the airplane 
inclined steeply downward. The airplane descends in 
a helix of large pitch and very small radius, the upper 
side of the airplane being on the inside of the helix, and 
the angle of attack on the inner wing being maintained 
at an extremely large value. 

Spinner. — A fairing, usually made of sheet metal and roughly 
conical or paraboloid in form which is attached to the 
propeller boss and revolves with it. 

Spiral instability. — The instability on account of which an 
airplane tends to depart from straight flight, by a com- 
bination of side slipping and banking, the latter being 
always too great for the turn. 

Splice (of a wooden member). — A joint of two or more pieces 
of wood in which one piece overlaps the other in such a 
manner as to maintain the strength. 

Spread. — (See Span.) 

Stability: 

Static stability. — A machine is statically stable if, when, 
slightly displaced by rotation about its center of gravity 
(as in wind tunnel experimentation), moments come 
into play which tend to return the machine to its normal 
attitude. 

Dynamical stability. — A machine is dynamically stable if, 
when displaced from steady motion in flight, it tends to 
return to that steady state of motion. 



NOMENCLATIVE FOR AERONAUTICS 43 

In a general way, the difference between static stability 
and dynamical stability is that the former depends on 
restoring moments and the latter on damping factors. 
Automatic. — Stability dependent upon movable control 
surfaces. The term "automatic stability" is usually 
applied to those cases in which the control surfaces are 
automatically operated by mechanical means. 
Directional. — Stability with reference to rotations about 
the normal axis; i. e., a machine possessing directional 
stability in its simplest form is one for which Nv is 
negative. Owing to symmetry, directional stability is 
closely associated with lateral stability. 
Inherent. — Stability of an aircraft due solely to the dispo- 
sition and arrangement of its fixed parts; i.e., that 
property which causes it, when disturbed, to return to 
its normal attitude of flight without the use of the con- 
trols or the interposition of any mechanical device. 
Lateral. — Stability with reference to disturbances involving 
rolling, yawing, or side-slipping; i.e., disturbances in 
which the position of the plane of symmetry of the air- 
craft is affected. 
Longitudinal. — Stability with reference to disturbances in 
the plane of symmetry; i.e., disturbances involving 
pitching and variations of the longitudinal and normal 
velocities. 

Stabilizer.— (See Tail Plane.) 

Stabilizer, mechanical. — A mechanical device to stabilize the 
motion of an aircraft. Includes gyroscopic stabilizers, 
pendulum stabilizers, inertia stabilizers, etc. 

Stable oscillation. — (See Oscillation.) 

Stagger. — The amount of advance of the entering edge of an 
upper wing of biplane, triplane, or multiplane over that 
of a lower, expressed as percentage of gap. It is con- 
sidered positive when the upper wing is forward and 



44 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

is measured from the entering edge of the upper wing 
along its chord to the point of intersection of this chord 
with a line drawn perpendicular to the chord of the 
upper wing at the entering edge of the lower wing, all 
lines being drawn in a plane parallel to the plane of 
symmetry. (Fig. 11.) 

Stagger wires. — (See Wires.) 

Stalling. — A term describing the condition of an airplane 
which from any cause has lost the relative air speed 
necessary for control. 

Standard pitch. — (See Pitch.) 

Static thrust. — The thrust developed by a propeller when 
the aircraft is held stationary on the ground. 

Station. — A term used to denote the location of framing 
attachment in a fuselage or nacelle (strut points in a 
trussed fuselage, bulkhead points in a veneer fuselage.) 

Statoscope. — An instrument to detect the existence of minute 
changes of atmospheric pressure, and so of small vertical 
motions of an aircraft. 

Stay. — A wire or other tension member; for example, the 
stays of the wing and body trussing. 

Step. — A break in the form of the bottom of a float or hull 
designed to assist in securing a dynamic reaction from 
the water. 

Stick control. — (See Control Stick.) 

Strand. — A species of wire made up of several individual 
wires twisted together. (There are usually 19 wires — 
a single wire as core, an inner layer of 6 wires, and an 
outer layer of 12.) 

Streamline. — The path of a small portion of a fluid, supposed 
continuous, commonly taken relative to a solid body 
with respect to which the fluid is moving. The term is 
commonly used only of such paths as are not eddying, 
but the distinction should be made clear by the context. 



NOMENCLATURE FOR AERONAUTICS 45 

Streamline flow. — The condition of continuous flow of a 
fluid, as distinguished from eddying flow. 

Streamline form. — A fair form intended to avoid eddying and 
to preserve streamline flow. 

Strut. — A member of a truss frame designed to carry com- 
pressive loads. For instance, the vertical members of 
the wing truss of a biplane (interplane struts) and the 
short vertical and horizontal member separating the 
longerons in the fuselage. (Figs. 1 and 12.) 

Strut, drag. — (See Drag strut.) 

Surface. — An aerofoil used for sustentation or control or to 
increase stability. Applies to the whole member, and 
not to one side only. 
Balanced. — A surface, such as a rudder, aileron, etc., part 
of which is in front of its pivot. 

Surface, main supporting. — A pair of wings, extending on the 
same level from tip to tip of an airplane; i.e., a triplane 
has three main supporting surfaces. The main support- 
ing surfaces do not include any surfaces intended 
primarily for control or stabilizing purposes. 

Suspension band. — The band around a balloon or airship to 
which are attached the main bridle suspensions of the 
basket or car. 

Suspension bar. — The bar used for the concentration of 
basket suspension ropes in captive balloons. 

Sweep back. — The angle, measured in a plane parallel to 
the lateral axis and to the chord of the main planes, 
between the lateral axis of an airplane and the entering 
edge of the main planes. (Fig. 16.) 

Tail boom. — A spar or outrigger connecting the tail surfaces 
and main supporting surfaces. Usually used on pushers. 
_ (Fig. 3.) 

Tail cups. — A steadying device attached by lines at the rear 
of certain types of elongated captive balloons. Some- 



46 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 




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NOMENCLATURE FOR AERONAUTICS 47 

what similar to a sea anchor. (Fig. 17.) Lobes have 
replaced tail cups to a large extent. 

Tail droop. — A deformation of the airship in which the axis 
bends downward at the after end. 

Tail heavy. — The condition of an aircraft in which, in any 
given condition of normal flight the nose tends to rise if 
the longitudinal control is released; i.e., the condition in 
which the pilot has to exert a push on the control stick 
or column to maintain the given condition. 

Tail plane. — A stationary horizontal, or nearly horizontal, 
tail surface, used to stabilize the pitching motion. Often 
called "stabilizer." (Fig. 10.) 

Tail setting, angle of. — (See Angle.) 

Tail skid.— (See Skids.) 

Tail slide. — The rearward motion which certain airplanes 
may be made to take after having been brought into a 
stalling position. 

Tail unit. — The tail surfaces of an aircraft. 

Tandem airplane. — (See Airplane.) 

Taxi, to. — To run an airplane over the ground, or a seaplane 
on the surface of water, under its own power. 

Toggle. — A short crossbar of wood or metal, having a shoul- 
dered groove, which is fitted at the end of a rope at right 
angles to it. It is used for obtaining a quickly detach- 
able connection with an eye at the end of another rope. 
(Fig. 18.) 

Tractor airplane. — (See Airplane.) 

Tractor propeller. — (See Propeller.) 

Trail rope. — The long trailing rope attached to a spherical 
balloon, to serve as a brake and as a variable ballast. 

Trailing edge. — The rearmost edge of an aerofoil or propeller 
blade. 

Trajectory band. — A band. of webbing carried in a curve 
over the top of the envelope of an airship to distribute 



48 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

the stresses due to the suspension. The use of trajec- 
tory bands was introduced in the Parseval airships. 
(Fig. 19.) 

Triplane. — A form of airplane whose main supporting sur- 
face is divided into three parts, superimposed. 

Turn indicator. — An instrument showing when the direction 
of the line of flight or the direction of the projection of 
that line on a horizontal plane is altering, and in its 
more refined forms, giving the rate of turn, in terms 
either of the angular velocity or of the radius of curvature. 

Unstable oscillation. — (See Oscillation.) 

Useful load.( — See Load.) 

Valve, automatic. — (See Automatic Valve.) 

Veneer.— Thin sheets or strips of wood. 

Venturi tube. — A short tube with flaring ends and a con- 
striction between them, so that, when fluid flows 
through it, there will be a suction produced in a side 
tube opening into the constricted throat. This tube, 
when combined with a Pitot tube or with one giving 
static pressure, forms a pressure nozzle, which may be 
used as an instrument to determine the speed of an air- 
craft through the air. (Fig. 21.) 

Virtual pitch.— (See Pitch.) 

Warp, to. — To change the form of a wing by twisting it. 
Warping is sometimes used to maintain the lateral 
equilibrium of an airplane. 

Wash. — The disturbance in the air produced by the passage 
of an aerofoil. 

Washin. — A permanent increase in the angle of attack near 
the tip of the wing. 

Washout. — A permanent decrease in the angle of attack near 
the tip of the wing. 

Weight, dischargeable. — (See Dischargeable Weight.) 

Weight, dry.— (See Dry Weight.) 



NOMENCLATURE FOR AERONAUTICS 49 

Weight per horsepower. — The dry weight of an engine 
divided by the normal horsepower developed at ground 
level. 

Wheel control. — (See Control Column.) 

Width ratio, total (propeller blade. — The product of blade 
width ratio by number of blades. 

Wind, relative. — (See Relative Wind.) 

Wind tunnel. — An elongated inclosed chamber, including 
means for the production of a substantially steady air 
current through the chamber. Models of aircraft or 
other objects are supported in the center of the airstream 
and their resistance and other characteristics when 
exposed to an air current of known velocity are deter- 
mined. The term includes those laboratories in which, 
as in the Eiffel type, there is an experimental chamber of 
much larger cross-section than the air current. 

Windmill. — A small air-driven turbine with blades similar 
to those of a propeller exposed on an aircraft, usually 
in the slip stream, and used to drive such auxiliary 
apparatus as gasoline pumps and radio generators. 

Window, inspection. — (See Inspection window.) 

Wing. — The portion of a main supporting surface of an air- 
plane on one side of the plane of symmetry; e.g., a biplane 
has four wings. 

Wing loading. — The weight carried per unit area of support- 
ing surface. The area used in computing the wing 
loading should include the ailerons, but not the tail 
plane or elevators. 

Wing resistance. (See Drag.) 

Wing rib. — A fore-and-aft member of the wing structure of 
an airplane, used to give the wing section its form and to 
transmit the load from the fabric to the spars. (Fig. 
20.) 



50 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Rib compression. — A heavy rib designed to have the above 
functions and also to act as a strut opposing the pull 
of the wires in the internal drag truss. (Fig. 20.) 
Rib, form. — An incomplete rib, frequently consisting only 
of a strip of wood extending from the leading edge to the 
front spar, which, is used to assist in maintaining the 
form of the wing where the curvature of the aerofoil 
section is sharpest. (Fig. 20.) 

Wing skid.— (See Skids.) 

Wing spars. — The principal transverse structural elements 
of the wing assembly of an airplane. The load is trans- 
mitted from the ribs to the spars, and thence to the lift 
and drag trusses. (Fig. 20.) 

Wing truss. — The framing by which the wing loads of an 
airplane are transmitted to the fuselage; comprises 
struts, wires, or tie -rods, and spars. 

Wire. — In aeronautics refers specifically to hard-drawn solid 
wire. 

Wires, antidrag. — Wires designed primarily to resist forces 
acting parallel to the planes of the wings of an airplane 
and in the same direction as the direction of flight. 

Wires, antilift. — Wires in an airplane intended mainly to 
resist forces in the opposite direction to the lift, and 
to oppose the lift wires and prevent distortion of the 
structure by overtightening of those members. 

Wires, drag. — All wires designed primarily to resist forces 
acting parallel to the planes of the wings of an airplane 
and opposite to the direction of flight. 
Internal drag wires are concealed inside the wings. 
External drag wires run from the wing cell to the nose of 
the fuselage or some other part of the machine. 

Wires, lift. — the wires which transmit the lift on the outer 
portion of the wings of an airplane in toward the fuselage 
or nacelle. These wires usually run from the top of an 



NOMENCLATURE FOR AERONAUTICS 

Trajectory J5&?zc/& .. 

M Mi 



51 



TotfU 



nc is 




fIC. 19 



■aSpors y &f'A Compress /om &i3 




No. zo 







pl<52l 



52 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

interplane strut to the bottom of the strut next nearer 
the fuselage. 

Wires, stagger. — Wires connecting the upper and lower sur- 
faces of an airplane, and lying in planes substantially 
parallel to the plane of symmetry. 

Yaw, angle of. — (See Angle.) 

Yawing. — Angular motion about the normal axis. 

Yawmeter. — An instrument giving by direct reading the 
angle of yaw. 

Yoke. — (See Control column.) 

Zero lift angle. — The angle between the chord and the rela- 
tive wind when the lift is zero. 

Zero lift line. — The position in the plane of an aerofoil section 
of the line of action of the resultant air force when the 
position of the section is such that the lift is zero. 

Zoom, to. — To climb for a short time at an angle greater than 
that which can be maintained in steady flight, the 
machine being carried upward at the expense of its 
stored kinetic energy. This term is sometimes used by 
pilots to denote any sudden increase in the upward 
slope of the flight path. 



CHAPTER II 

Explanations and Definitions of Various Other Terms 
Used in Connection with Aircraft, Etc. 

Q. How many kinds of resistance are there to an airplane 
in flight? 

A . Two kinds of resistance, wing resistance and all other 
resistances being known as parasite resistance. 

Q. How many kinds of stabilities are there? 

A. Seven, as follows: Static, Automatic, Inherent, Dy- 
namical, Directional, Longitudinal and Lateral. (See Nomen- 
clature for definition of each.) 

Q. Which way does the center of pressure travel when a 
machine is in a climb? 

A. The center of pressure travels forward until machine 
is climbiDg at too great an angle when the center of pressure 
travels rapidly towards the trailing edge and the machine 
will go into a stall. 

Q. What are the results obtained by the gap being of 
the same distance as the length of the chord? 

A. All things considered, the best results are obtained 
when gap equals chord. In order to eliminate interference 
entirely the gap should be 1.25 the length of chord. This 
would necessitate longer struts, longer load and lift wires, 
thereby increasing resistance as well as adding additional 
weight. 

Q . What are the advantages and disadvantages of stagger? 

53 



54 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. The advantage of stagger is that the lift-drift are 
both increased by about 5 per cent. It is said the best 
method of stagger is to place the upper leading edge about 
two-fifths the length of chord in advance of the leading 
edge of the lower plane. This improvement is equivalent 
to that which would accrue if the biplane spacing of the gap 
was 1.25 per cent of the chord. An additional advantage 
is that it offers a better range of vision to the occupants. 
The disadvantage is that the strength of inclined struts to 
vertical load is decreased. 

Q. What is center of gravity? 

A. The point of a body about which all portions are 
balanced. 

Q. What is center of lift? 

A. The mean of all the centers of pressure. 

Q. What is the center of pressure? 

A. A fine taken across the surface, transverse to the 
direction of motion and about which all the air forces may 
be said to balance, or through which they may be said to act. 

Q. What is center of thrust? 

A. A point or line along which the thrust of the propellers 
is balanced. (Center line of propeller.) 

Q. What is the usual aspect ratio used? 

A. The span is usually five to eight times the chord, the 
ratio of 6 to 1 being generally used, and the higher ratios 
given increase the efficiency of a wing because the loss of 
efficiency due to the air spilling off the wing tips is reduced 
by increasing the aspect ratio. 



EXPLANATIONS AND DEFINITIONS 55 

Q. What is propeller torque? 

A. The effect of the reaction of the revolving propeller 
upon the equilibrium of the airplane is to cause a banking 
couple unless twin propellers are used. The amount of this 
couple is well within the pilot's control and it is only its 
variation which requires attention. 

Q. What is a variable load? 

A. A variable load consists of fuel and oil. This load is 
located near the center of gravity so as to have the least 
effect on the stability of the machine due to variability. 

Q. What is meant by caviation? 

A. Effect of revolving a propeller at an excessive speed 
for its pitch and diameter, creating a "hole" so to speak. 
The fuel, water, or air is carried around by the blades of the 
propeller in the same plane instead of being thrust back. 

Q. What is a castellated nut? 

A . One that is slotted to take a cotter pin passing through 
a hole in the bolt. So called from its resemblance to an 
ancient castle wall. 

Q. What is meant by clockwise? 

A. An engine that turns its shaft to the right (direct 
drive), or in the same direction as a clock hand rotates. 

Q. What is meant by anti-clockwise? 

A. An engine that turns its shaft to the left when 
viewed from the propeller end. Also termed a left handed 
engine. 

Q. What is meant by critical speed? 



56 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. Rate of travel at which an aeroplane just propels and 
sustains itself in the air. 

Q. What is lee-way? 

A. Movement at an angle to the course being steered, 
caused by the lateral drift of the atmosphere or by centrif- 
ugal force acting on the airplane in rounding a turn; also 
the angular deviation from a set course over the earth, due 
to cross currents of wind, also called drift, 

Q. What is a pylon? 

A . A pole placed on an aviation field to mark the course, 
also a mast or pillow serving as a marker of a course. Captive 
balloons are also used as pylons. 

Q. What is spotting? 

A. Noting the fall of shells from an airplane or balloon 
and reporting to the batteries necessary corrections in the 
range. 

Q. What is dynamic thrust? 

A . The work done by the propeller in forcing the airplane 
ahead. It equals the weight of the mass of air acted upon 
per second, the slip velocity in feet per second. 

Q. What is meant by the term decalage? 

A. This is the difference between the degrees of the 
angle of incidence in the upper and lower planes, in other 
words, if the upper plane has three (3) degrees angle of 
incidence, and the lower plane has two (2) degrees angle of 
incidence, it would be stated that the machine would have 
one (1) degree of decalage. 

Q. What is meant by the term cathedral angle? 



EXPLANATIONS AND DEFINITIONS 57 

A. This is just the opposite of dihedral angle, and in 
some later type machines is placed in the lower wings of 
planes. 

Q. What is an engine section panel? 

A. The engine section panel is the panel directly above 
the fuselage or boat. This section usually contains a gravity 
tank for supplying gasoline to the engine. 

Q. What are sidewalk panels? 

A. Sidewalk panels are the lower panels adjacent to the 
hull of a flying boat or the fuselage of a pontoon type machine. 
They are portable in some types of machines, and in others 
they are built over the sidewalk beams, which in turn are 
built into the boat (and are not portable.) They derive 
their name from the fact that it is necessary in most instances 
to walk on same in getting in and out of the machine. Some- 
times they are wholly covered with veneer for additional 
strength, and in other cases, only a section is covered with 
veneer to walk upon. 

Q. What is an intermediate panel? 

A. An intermediate panel is the panel adjacent and con- 
nected to the sidewalk panel in the lower plane, which in 
turn has the lower outer plane connected to the outer end 
of the intermediate panel; in the top plane the intermediate 
panel connects to engine section panel on inboard end, and 
to the outer end is connected the upper outer panel. 

Q. What is an outer panel? 

A. An outer panel is the outmost panel on each side, 
and is described as the right upper outer, left upper outer, 
right lower outer, and left lower outer. 



58 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. What is meant by flight path? 

A. The path of the center of gravity of an aircraft with 
reference to the earth. 

Q. How many forces are there acting upon an airplane 
in flight? 

A. There are four forces: (1) The weight of the machine 
acting vertically downward through its center of gravity. 
(2) The aerodynamic lift of the wings and other supporting 
surfaces acting through the center of pressure. (3) The 
total head resistance of the whole machine which acts in 
a direct parallel to the direction of motion of the machine 
through the center of resistance. (4) The propeller thrust 
acting through the center of thrust. 

Q. Where should the center of pressure come on a well 
designed wing panel? 

A. The center of pressure for the range of flying angle 
used should have a stable position, and, further, the range 
of movement along the chord should be a minimum. The 
center of pressure in a good wing section should lie between 
0.3 and 0.45 of the chord distance from the leading edge at 
all incidences used in flying. 

Q. Does the suction and pressure on a wing panel remain 
the same at all angles of incidence? 

A. The combined loading remains at 100 per cent, but 
the greatest upper surface load or suction is when the angle 
of incidence is at zero, at which point the upper surface 
load would be 92 per cent and the lower surface load 8 per 
cent and the change between upper surface load and lower 
surface load will occur as follows, in accordance with the 
angle of incidence: 



EXPLANATIONS AND DEFINITIONS 



59 



ANGLE OF INCIDENCE 


UPPER SURFACE LOAD 


LOWER SURFACE LOAD 




per cent 


per cent 





92 


8 


2 


82 


18 


4 


74 


26 


6 


74 


26 


8 


72 


28 


10 


69 


31 



CHAPTER III 

Description of Heavier-Than-Air Craft and Their 
Construction in General 

Q. How many types of heavier-than-air craft are there? 

A. There are four types: Land planes, seaplanes, flying 
boats and amphibious planes. 

The following is a description of each: 

A land plane has a body known as a fuselage to which one, 
two, or three pairs of wings are connected thereto. It has 
a structure called a chassis to which two or more wheels are 
connected with shock absorbers attached to the axles in 
order that the machine can land without damage and roll 
over the ground until its momentum or headway has expended 
itself. On the under side of the rear end of this fuselage is 
an ash or oak stick, known as a tail skid, which is covered 
with a metal strip which slides over the ground after the 
machine has landed. The fuselage referred to, if a single 
engine machine, has the engine located in the forward part 
of same, the gas tank in the rear of engine, one pilot seat 
in the rear of gas tank and another pilot seat in the rear of 
first seat, these being known as the front and rear cockpits. 

A seaplane has a body known as a fuselage which carries 
engine, gas tank, two pilots, or pilot and observer, or pilot 
and student as the case may be, and has one or two pontoons 
connected thereto by the means of struts for landing and 
getting off the water. Seaplanes with only one pontoon 
usually have installed on the under side of the lower wings 
on the outermost ends what is known as a wing tip float. 
This prevents the wings from dipping in the water in getting 
off or making a turn on the water when a side gust may tend 

60 



DESCRIPTION AND CONSTRUCTION 61 

to over-balance the machine somewhat, and the wing-tip 
floats, being hollow and buoyant offer a lift, thereby prevent- 
ing wings from being submerged or struck by choppy seas. 
Seaplanes with twin pontoons do not have wing tip floats. 

A flying boat consists of a light weight but strongly con- 
structed covered over boat with a "Y" shape bottom. 
Attached to this boat usually are two pair of wings, upper 
and lower, and in the hull of this boat is carried the gas and 
oil tanks, the pilot seats, which are usually two seats arranged 
side by side, gunner's cockpit forward or aft of the pilot's 
cockpit, as the case may be. The engine is supported by 
struts in a single engine machine overhead in this boat 
directly on the center line, or if twin engines, both being 
supported by struts between the lower and upper planes to 
the right and left of the hull respectively. 

An amphibious plane is somewhat similar to a flying boat 
except it has a retractable chassis whereby it can be used in 
taking off on land and landing on water or vice versa. In 
other words, it can be used for both land and water purposes. 

Q, How many wings are there on a heavier-than-air craft? 

A . One set or pair of wings on a monoplane ; two pairs of 
wings on a biplane; three pairs of wings on a triplane, and 
four pairs of wings on a quadruplane. Triplanes and quad- 
ruplanes are not used generally, the biplane and monoplane 
types being preferred. 

Q. What is a rudder and how constructed? 

A. A rudder is a vertical plane made of metal tubing, 
braced with spruce members and fabric covered, the upper 
portion being hinged to the vertical stabilizer and the lower 
portion to the fuselage or tail post of flying boat. The 
movement of rudder to right or left causes the machine to 
go in that direction, as the case may be. 



62 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. What is an elevator and how constructed? 

A. An elevator is a horizontal plane placed in the rear 
of and hinged to the horizontal stabilizer. In most cases 
they are made in pairs either right or left elevator, and some- 
times the spar on the leading edge is of one piece and the 
plane is built up with an opening in the center, in order 
that the rudder may turn to right and left. Whether there 
are one or two elevators, they both have the same movement, 
up and down together, in order that the machine may be 
caused to rise or glide, as the case may be. The elevation 
of the elevators causes the machine to rise and the depression 
of same causes the machine to glide downward. 

Q. How is an N-9 fuselage constructed? 

A, An N-9 fuselage is generally constructed of four ash 
members from the rear of the after cockpit forward, and 
from the rear of the after cockpit aft of spruce, being spliced 
together in this section These members are known as 
longerons, the forward ends of which are connected to a 
metal lightened flanged plate, known as a nose plate. The 
after ends of these members are secured to a vertical post 
of spruce that is known as a tail post. These four longerons 
are held apart vertically by spruce struts known as fuselage 
struts. In the wake of pontoon strut connection, the fuse- 
lage struts are of considerably larger sections than elsewhere. 
The upper and lower longerons are held apart by the means 
of transverse spruce braces, the whole being tied together 
by cross brace wires; between each section forward of the 
after cockpit by 19 strand galvanized wire, and aft of the 
rear cockpit by solid tinned wire, the reason for the difference 
in these wires being that the rear part of this fuselage is 
not subject to the same strains through shock and vibration 
that the forward and engine sections are. In the forward 
part of this fuselage there are two laminated longitudinal 



DESCRIPTION AND CONSTRUCTION 63 

pieces of wood known as engine bearers. The forward end 
of these bearers rest in the nose-plate previously mentioned. 
The rear ends of these bearers rest on a cross-brace and are 
secured by the means of "U" bolts. These bearers are 
usually of three laminations, the center being made of spruce, 
and the top and bottom laminations being made of ash. At 
the point in these bearers which bolt holes are bored to 
secure to engine base the bearers are copper flashed. This 
flashing is done by bending light copper around the bearer, 
which is tacked and secured with brass tacks with the heads 
soldered. Copper is not always applied, being often re- 
placed by large washers under bolts. In the rear of the 
engine is the gas tank which is secured in place by the means 
of metal straps. In the rear of this, running fore and aft 
on each side, secured to the vertical braces, is what is known 
as the seat rail, the pilot seat being connected thereto, both 
forward and rear seats resting thereon, and connected to 
the lower longerons in the wake of both cockpits are floor 
board supports on which the floor boards in the cockpits 
rest, There is nothing installed in the remaining rear sections 
in the fuselage. The forward part of the machine, in the 
wake of engine and tank sections, are covered with sheet 
aluminum known as cowling, the sides and bottom of the 
remaining part of the fuselage being covered with fabric, 
grade "B", linen or cotton. Installed in the cockpits is a 
rudder bar for operating the rudder by the feet, also a control 
yoke for operating the elevators, and a control wheel mounted 
on the control yoke for operating the ailerons. On the top 
side, in the rear of the after cockpit is a light frame-work, 
fabric covered, known as streamlining. 

Q. How is a wing panel constructed? 
A . A wing panel is constructed of two main spars, usually 
of spruce, one known as the front spar and the other as the 



64 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

rear spar. Along these spars are distributed a number of 
ribs, the inner end of wing panel having what is known as 
box ribs which consist of two ribs about a half an inch apart, 
not lightened. These are followed by what are known as 
former ribs, which are made of white pine, lightened by 
having elliptical and round holes cut in same. In the lighter 
type machines, in the wake of strut connections, and where 
the terminals for internal brace wiring is secured, there is 
one unlightened rib known as a compression rib. In larger 
types of machines this compression member is also made 
of round spruce, being tapered at the ends and swelled 
in the middle ; also in some types of machines this compression 
member consists of a steel tube. Opposite, and placed 
intermediately between these former ribs on the forward 
side of the front spar is what is known as a nose rib. 
In the rear of the rear spar, and placed opposite the various 
main ribs, is what is known as the tail rib. The tail ribs 
are held in place, as well as the main, by the use of what is 
known as a cap strip. These cap strips are of spruce, and 
extend from midway of the top side of the front spar, across 
the rear beam, and over the top edge of the tail rib, and 
terminate at what is known as the trailing edge. On the 
under side of these ribs is a similar cap strip of spruce. These 
cap strips are ploughed out on one side for a depth of about 
J inch, where they fit over the top and bottom edges of the 
ribs. They are secured to ribs by the use of glue, brass or 
galvanized nails, and screws. Between the lightened holes 
in all former ribs, the remaining wood is reinforced by the 
use of small pieces of birch veneer, which are glued thereto 
and secured with six brass tacks clinched. 

The cap strips over the compression ribs are of a little 
wider dimension than those over the former ribs. Along 
the top of the front spar, on the forward edge, is secured a 
strip of the same thickness as the cap strips which is made 



DESCRIPTION AND CONSTRUCTION 65 

of spruce and is known as the filler strip. On the forward 
edge of the nose ribs there is secured to these ribs what is 
known as a nose moulding; this is hollowed out on one side 
to fit the leading edge of the nose ribs. Secured to this nose 
moulding, and extending back to the filler strip on the front 
spar, is a layer of three-ply veneer. On the outmost ends 
of the wing panels the spars are tapered down to a lesser 
dimension than at main body of the spar, it not being essential 
at this point for the spars to be of the same dimension as 
elsewhere, as a lesser load or strain is introduced at this point. 
Running from the leading edge and to the trailing edge around 
the end of this panel is what is known as an end bow, which 
is steamed and bent to the curvature required in the design; 
this is connected to the nose moulding and the metal trailing 
edge in a wing panel. The trailing edge of this panel is 
made of f inch diameter steel tubing mashed slightly ellip- 
tical, having a copper strip brazed thereto in the wake of each 
trailing rib. These copper strips in turn are nailed to the 
top and bottom cap strips, thus forming the trailing edge 
of the wing panel. It is to be noted that intermediate panels 
do not have the en# bow previously mentioned, but have 
box ribs on each end of the panel. A diagonal brace made 
of spruce is placed between the junction of the end bow and 
rear wing spar to stiffen the curvature at the outmost end. 
All wing panels are braced internally by the use of solid 
tinned wire running cross-wise between compression ribs. 
This makes the structure more rigid, and takes care of the 
drift load when machine is in flight. 

Q. What are stringers? 

A. Stringers, as used in aircraft construction, consist of 
longitudinal pieces of spruce or ash running parallel to the 
keel to which bottom planking is secured. Also, stringers 
are used in the bottom frame construction of pontoons and 



66 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

those to which the curved deck is secured are known as deck 
stringers. Stringers are also used to stiffen the ribs in a 
wing panel being from J to f inch in diameter and run parallel 
to the front and rear spars, passing through the former and 
compression ribs near top and bottom in the center of panel, 
being secured at one end to the box ribs and to the end bow 
by means of small blocks, glue being applied to same where 
it passes through various ribs. 



CHAPTER IV 

Woods Used in the Construction of Aircraft, Their 
Defects, Method of Dry Kilning, Etc. 

Q. What woods are used in the construction of airplanes? 

A. The principal woods used in the construction of air- 
craft are spruce, ash, white pine, mahogany, Spanish cedar, 
basswood, Port Orford cedar, white cedar, birch, rock elm, 
white oak, and fir. 

Maple is being used for forms. Rock elm, ash, and white 
oak are considered most practicable for sharp bends, but 
owing to the scarcity of rock elm and the added weight of 
white oak over that of ash, the ash is used almost exclusively 
where considerable strength is required. There are three 
kinds of mahogany; namely, Philippine, Cuban, and Hon- 
duras, the latter being considered best for aeroplane work 
on account of its closeness of grain, more flexibility, contains 
less defects, and is not as hard as the Cuban or Philippine 
mahogany. 

Haskell veneer is used extensively in aircraft, and it is 
made in single, two, and three ply, or more if required. Fir 
sometimes may be substituted for spruce, but the objection 
thereto is the additional weight. 

Basswood is considered the best wood for floors, although 
pine is being used; basswood and pine are interchangeable 
for keelsons. 

Hickory can be used to advantage on such parts as foot 
controls, Deperdussin controls, and false keels where ash 
is now used. Also pontoons struts are being made of hickory 
and are considered better material for this purpose than any 
other wood. 

67 



68 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Maple is an ideal wood for molds and patterns, it being 
very hard, close grained, and tough, and it will not warp 
and check like other woods. 

Birch, other than that used in the manufacture of several 
ply veneer, is used singly as a stiffner on ribs in a wing panel 
between lightened holes, being glued and bradded thereto. 
Where birch is used in the manufacture of veneer, it is used 
for the outer plys and in the case of three-ply veneer the 
interior may be mahogany or poplar with the grain running 
at right angles to the grain in the outer ply. In some three 
ply veneer, the outer plys are made of mahogany and the 
interior of poplar. 

It being a very difficult matter to describe the appearance 
of various woods so that a layman may understand same, a 
brief description of the various woods is given in order that 
one may have a slight knowledge of these woods and this 
may be of some assistance. 

Mahogany is a hard wood and is of a reddish-brown in 
color and very close grained. 

Birch is a close grained hardwood of a pale yellowish color. 

Pine is a white soft wood, the cells being closely woven 
together. 

Ash is a hard wood distinguishable by its long, straight, 
white grain. 

White Oak is a hard wood of close straight grain, similar 
in appearance to white ash, except that it is darker in color 
and heavier. 

Rock Elm is a hard wood similar in appearance to ash, 
but the fibers are somewhat closer and the wood is more 
tough. 

Spanish Cedar is very light in weight and very soft. It 
has a very pale, reddish color. The grain is similar in 
appearance to mahogany, the grain being very close. 



WOODS USED IN CONSTRUCTION 69 

Basswood is very similar in appearance to white pine. It 
is somewhat stronger and a little heavier, and is very hard 
to detect from white pine after a coating of varnish is applied. 

Port Orford Cedar and White Cedar are both practically 
the same in appearance, being of low specific gravity. They 
are both closely woven grain, not used to much extent at 
this time for aeroplane work. 

Q. What are defects in wood? 
A. Defects in wood consist of: 

(a) Large and unsound knots 

(b) Cross or diagonal grain 

(c) Shakes 

(d) Spiral grain 

(e) Pitch pockets 

(f ) Dry rot and dote spots 

(g) Wavy grain 
(h) Worm holes 

(i) Low density of wood as in spruce below 0.36 

specific gravity 
(j) Chipped grain 
(k) Torn grain 
(1) Brashness 
(m) Case hardening 
(n) Season checks 
(o) Stained sap 

NOTES 

(a) Knots: Pin knots of about the size of a lead pencil are 
allowed, proportional to the width of piece. Edges must 
always be free of knots. The effect of knots depends upon 
their location with respect to the stresses to which the piece 
shall be subjected, as well as upon their size and character. 



70 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

None but sound knots, firmly attached, should be permitted. 
Obviously, knots of any considerable size can not be allowed 
in any aeroplane parts because the parts themselves are 
comparatively small in cross sections. Since the weakening 
effect of knots results from their disturbance of normal 
arrangement of fibers, their seriousness can best be decided 
from a consideration of the grain. 

(b) Certain defects may be allowed in conjunction with 
the use of cross-grained material. Between straight grain 
(1 in 25) and a slope not steeper than 1 in 20, J inch knots 
are allowable when not nearer together than 10 inches. 
Where strength is so unimportant that a slope of 1 in 15 is 
permitted, even larger knots up to J inch are harmless, pro- 
vided they are not closer than 20 inches and do not affect 
the edge grain. 

(c) Shakes: Shakes are sections in the wood fiber, either 
tangentially along the annual rings, or in a radial plane 
parallel to the axis of the wood fibers. They are the result 
of an actual rupture due to heavy winds, and sometimes 
caused by the felling of the tree. It requires a very minute 
inspection to locate this defect sometimes as the opening 
may not be visible, and again it may be only discolored. 
This defect can sometimes be determined by sounding the 
wood with a mallet, if there should be any question in the 
inspector's mind as to its soundness. 

(d) Spiral Grain: Under normal conditions of wood 
growth, the axis of the principal wood cells or fibers are 
parallel to the axis of the tree, but frequently in spruce and 
other species the cells are inclined so that a line through the 
axis of a number of cells takes a spiral course. Spiral grain 
reduces the strength of wood considerably and a deviation 
from straight grain of more than 1 inch in 20 inches is sufficient 
for its rejection. Those familiar with spiral grain can detect 
it with the naked eye in rough green lumber by the direction 






WOODS USED IN CONSTRUCTION 



71 



of the long shaggy fibers. The direction of the grain may be 
ascertained by picking at the fibers with a knife or splitting a 
small piece with a chisel. The most recently developed 
method and the surest used for detecting spiral grain is to 
place a few drops of ink either red, blue or green, on the 
tangential face and notice the direction which the capillary 
action draws the ink along the fiber. 

(e) Pitch Pockets: Pitch pockets are openings between the 
annual rings which contain rosin either in liquefied, solidified, 
or' granulated form. They are not as detrimental to the 
strength of a piece of material as ordinarily supposed, unless 
they are unusually large and accompanied by curly grain. 
The maximum length of a pitch pocket permitted is three 
inches and the maximum depth one-quarter inch. If pitch 
pockets are in the same annual rings they may not be closer 
together than 40 inches; in other portions of the section this 
distance may be 10 inches and 20 inches respectively.' 

The following is a table showing a combination of defects 
allowable with different slopes of grain: 





KNOTS 


PITCH POCKETS 


ALLOWABLE SLOPE IN GRAIN 
NOT EXCEEDING 


Maximum 
diameter 
permitted 


Minimum 
distance 
between 
any two 


Maximum 

length 
permitted 


Maximum 

width 
or depth 
permitted 


1 inch in 25 


inches 

l 

4 

8 
1 
2 


inches 

10 
12 
20 


inches 

14 

2 
3 


inches 

l 

8 

1 
4 

1 
4 


1 inch in 20 

1 inch in 15 



(f) Dry Rot and Dote Spots: Dote is an incipient form 
of decay in wood markedly affecting the strength of the pieces. 
Dote and dry rot usually are found at the heart center; it 
may be only a quarter of an inch or less in diameter, but upon 
cutting an end off the piece it may be an inch to several 



72 



inches in diameter. It is light, punk, brash and lifeless, and 
can be determined by weighing against a piece of known 
good material as it is very light in weight. 

(g) Wavy Grain: Wavy grain are dips and curves in the 
annual rings; while this defect is not hard or difficult to see 
it is exceedingly hard to estimate the extent to which the 
piece is impaired. Where all of the annual rings are affected 
by the wave or dip, the deviation of 1 inch in 25 should 
govern rejections as in diagonal and cross grain. 

(h) Worm Holes: Worm holes should be the cause for 
rejection of any material used in the construction of aircraft, 
because they impair the strength and the number and extent 
of same can not be predetermined or detected. 

(i) Low Density of Wood: Low density of woods, as spruce 
below 0.36 can not be used. Wood of low density as spruce 
which has a specific gravity of less than 0.36 based on oven 
dry weight and oven dry volume must not be used for such 
aircraft parts as wing spars, struts, etc., where high strength 
is required. Where the moisture content of the wood is 
known, its density can be readily determined by its weight. 
Within a given species the density of the wood is governed 
by the proportion of summer wood cells in each annual growth 
ring; these summer wood cells have heavier walls and are 
easily distinguished by their darker color. 

(j) Chipped Grain: This defect occurs in surface lumber 
when portions of the wood fiber are chipped out during 
machining, producing depressions in the surface of material. 
These chipped areas are often the result of poor manufacture 
and do not necessarily indicate irregularity of the grain and 
practically speaking, is only a minor defect. 

(k) Torn Grain: Torn grain differs from chipped grain 
in that it usually occurs around knots or in portions of the 
surfaces where there are irregularities in the grain, such as 
waves and curls. Torn grain is always an indication of 



WOODS USED IN CONSTRUCTION 73 

unusual growth and usually signifies an inferior piece of 
wood, from the standpoint of strength. 

(1) Brashness: Brashness is a form of decay found in ash 
and oak. It is a kind of dry rot; it is lighter in weight than 
a piece of wood of the same material in its normal condition, 
and should not be used any place where strength is required ; 
when broken it will break sharp and snappish. It contains 
very little moisture and its specific gravity is way below the 
average. Brashness is sometimes caused by being piled for 
a long period of time. 

(m) Case Hardening: Case hardening of lumber is 
brought about by too rapid drying, causing the surface to 
diy more rapidly than the moisture can pass to it from the 
interior. Case hardened lumber when resawed will invar- 
iably cup towards the inside if the interior of the lumber is 
too dry. Case hardening can practically be prevented by 
regulating the humidity so that the evaporation from the 
surface does not take place too rapidly. Case hardened wood 
is not permitted in the use of aircraft as its strength has been 
reduced. 

(n) Season Checks: Season checks are small cracks here 
and there on a piece of material and their depth cannot be 
determined, therefore checked material is not permitted in 
aircraft. In order to prevent checking of material while 
being kiln dried, the ends of same are given a coat of asphaltum 
paint. 

(o) Stained Sap: All stains and discolorations should be 
regarded with suspicion and carefully examined. It must 
be remembered that decay often spreads beyond the dis- 
coloration it causes, and that pieces adjacent to discolored 
area may already be infected. On the other hand, not all 
stains and discolorations are caused by decay of the wood. 
The blue sap stain of some hard woods and of many conif- 
erous woods, including spruce, and the brown stain of sugar 



74 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

pine are not caused by decay producing organism and do 
not weaken the wood. 

It is to be noted that plywood is used to a great extent in 
the construction of aircraft and the following is a list of 
wood that may be used in plywood construction : 

Basswood (Northern) Redwood 

Beech Spanish cedar 

Birch Spruce 

Cherry Sycamore 

Fir (grand, noble, or silver) Western hemlock. 

Mahogany (true and African) White elm 

Maple, (hard and soft) White pine 

Red gum Yellow poplar 

The veneer must be sound, clear, smooth, well manu- 
factured stock of uniform thickness and free from injurious 
defects. Sap streaks and sound pin knots are not considered 
defects. Discolorations will be allowed. The veneer may 
be rotary cut, sliced or sawed. 

Only certified glue or cement or certified casein or certified 
blood albumen which will meet the tests specified may be 
used. 

The finished plywood should be dried to a moisture content 
of 9 to 11 per cent. Drying to excessively low moisture 
content induces excessive warping in panels. 

A good test for the best grade plywood is to soak same in 
water for ten days or boiling same for eight hours. The 
following covers the tests required by the Department for 
plywood. 

Shear Test: The strength of the glue joint shall be tested 
dry, wet after boiling in water for eight hours, and wet after 
soaking in water at room temperature for ten days. Fifteen 
test specimens shall be cut from a single panel, five for each 
of the three shear tests specified above. The ends of the 
specimen shall be gripped in the jaws of a tension-testing 






WOODS USED IN CONSTRUCTION 



75 



machine and the load applied at a speed of less than J inch 
per minute. 

The shear values for grades A and B plywood must give 
average loads equal to those given in table below. The 
average load in a given case is the average of the five speci- 
mens cut from the panel. All specimens giving 100 per cent 
wood failures below the load specified below will be rejected 
in computing the average. All failures above the specified 
load and all showing partial or complete glue failures will be 
included in the average. 





GRADE A PLYWOOD 






Cores 
xe inch or 

less 
thickness 


Cores over 

T V inch 
thickness 


GRADE B 
PLYWOOD 


Tested dry 


lbs. pei 
sq. inch 

325 
200 
200 


lbs. per 
sq. inch 

300 
180 
180 


lbs. per 
sq. inch 

225 


Tested while wet after 10 days soak- 
ing in water at room temperature. . 

Tested while wet after 8 hours boil- 
ing in water 


90 
65 



Q. What are the mechanical and physical properties of 
wood? 

A. Wood differs from other structural materials in a 
great many ways, and the maximum efficiency in its use 
demands a thorough knowledge of the properties of wood 
and of the factors which influence those properties. 

In some instances, specimens from different pieces of the 
same three have been found to show considerable difference 
in strength. In most cases, however, the wood of the highest 
specific gravity has the best mechanical properties regardless 
of its position in the tree. Where this is not the case, the 
toughest and most shock resistant material is found near the 



76 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

butt. Above a height of 10 or 12 feet, variation of mechan- 
ical strength corresponds to the variation of specific gravity. 

Among many of the hardwood species, material of very 
rapid growth is usually above the average in strength prop- 
erties. Noticeable exceptions to this are found, however, 
and rapid growth is no assurance of excellence of material 
unless accompanied by a relatively high specific gravity. 
This is particularly true of ash. In the coniferous species, 
material of very rapid growth is very likely to be quite brash 
and below the average strength. 

A piece of clear, sound, straight grain wood of any species 
is not necessarily a good stick of timber. To determine the 
quality of an individual stick by means of mechanical tests 
is extremely difficult, because the variation in strength of 
timber due to variation in moisture content, temperature, 
speed of test, et cetera, is so great. 

A specific gravity determination is relatively simple to 
make, and it is probably a better criterion of all of the qual- 
ities of the piece than any single mechanical test which is 
likely to be applied; also the specific gravity determination 
need no adjustments such as would be necessary on account 
of the various conditions of a mechanical test. 

When a piece of green or wet wood is dried, no change in 
mechanical properties takes place until the fiber saturation 
point is reached. 

AIRPLANE SPRUCE 

General Specifications 

1. Airplane spruce shall be divided into the following 
grades and shall conform to the requirements specified: 
I. Western spruce (Sitka) Picea sitchensis. 

(a) Class A (wing beam stocks). 

(b) Class B (long clears). 



WOODS USED IN CONSTRUCTION 



77 



II. Eastern spruce (Picea canadensis, Picea rubbis). 

(a) Class A stock. 

(b) Class B stock. 

(c) Class C stock. 

General for Eastern and Western Spruce 

2. (a) Airplane spruce shall be purchased as western or 
eastern spruce in accordance with the specifications given 
separately below for each kind. 

(b) All lumber shall be straight grain, sawed fair and full 
to sizes given. Allowance will be made for ordinary shrink- 
age of partly seasoned lumber, but no lumber will be accepted 
which in the inspector's opinion will not finish when fully 
seasoned to the following dimensions: 



GREEN (ROUGH SAWED)* 


FINISHED (PLANED FOUR SIDES)* 


Thickness 


Widths (inches) 


Thickness (inches) 


Widths (inches) 


inches 
1 to 2 | 


4 to 1\ 
8 to 12 

4 to 1\ 
8 to 12 


ftolf | 
11 to 3f | 


3fto 7 


2\ to 4 | 


1\ to 11| 

3| to 7 
71 to llj 



* Bright sap is no defect. 

All lumber to be manufactured from five and healthy 
trees. No material to be accepted which is cut from trees 
dead on the stump. 

Dimensions 

All dimensions shall be full. 
Thickness shall be in increments of \ inch. 
Widths shall be in increments of \ inch. 
Lengths shall be in increments of \ foot. 



78 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

3. Fractions of a foot are to be treated as follows: 
Even half feet will be alternately counted out and allowed 

as a whole foot. Fractions under half foot will be dropped ; 
fractions over a half foot will be allowed as a whole foot. 
Tapering lumber will be measured at one-third from the 
narrow end. Flitch-sawn lumber will be measured on the 
narrow face, under the bar at the middle of the length. 

Inspections 

4. Inspection to be at point of manufacture unless other- 
wise specified. The inspector shall have free access to all 
parts of the mills where this lumber is being manufactured, 
and shall be afforded every facility to satisfy himself that the 
lumber conforms to these specifications. 

EASTERN SPRUCE 

General 

Class A. To be sound, straight-grained white or red spruce, 
either vertical or slash sawn, practically clear of all knots, a 
few scattering tight red or white pencil knots only being al- 
lowed, providing they do not injure the strength of the piece 
and are located as to allow for clear cuttings full length, 4 
inches and up wide. 

Red or black rot, wind shake, season checks, and cross 
grain at an angle of more than 1 inch in 20 inches, pitch pock- 
ets, glassy heart, or any other defect tending to injure the 
piece for the purpose intended will not be allowed. 

Dimensions 

Dimensions. To be 18 feet and up long, 4 inches and up 
wide; 2, 2|, 3, 3| and 4 inches thick. 



WOODS USED IN CONSTRUCTION 79 

Class B. To conform to the general rules for Class A and 
to be 14 to 17 feet long, 4 inches and up wide. In general, 
this material shall run 2 inches, 2J inches, 3 inches, and 4 
inches in thickness, but shall include pieces 1| inches and 
1| inches thick of 14 feet and over in length. 

Class C. To conform to the general rules for Class A and 
to be 8 feet to 13 feet long, 4 inches and up wide. In general, 
this material shall run lj inches, 1J inches, 2 inches, 2\ 
inches, 3 inches, 3| inches, and 4 inches in thickness, but shall 
include pieces of 1 inch in thickness irrespective of length 
over 8 feet. 

WESTERN SPRUCE 

General 

To be sound straight-grained Sitka spruce material, prac- 
tically clear four sides, either vertical or slash sawn. Bright 
sap, knots, or equivalent burls \ inch or less in diameter and 
narrow pitch pockets and bark seams li inches in length 
will not be considered defects. The general direction of the 
grain shall not deviate from the longitudinal axis of the piece 
at a greater angle than 1 in 20. 

In pieces showing less than six growth rings per inch, re- 
jection or acceptance shall be based on the specific gravity 
of the piece, which shall be not less than .36. 

Class A. Wing Beam Stock. Size specifications to accom- 
pany order. 

Class B. No. 1. Clears. Lumber of this grade to be 2 inches 
or more in thickness, 4 inches or more in width, and from 10 
to 18 feet in length. Eighty-five per cent of this grade to be 
over 2 inches in thickness. 



80 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

AIRPLANE ASH 

Use 

1. This specification covers the requirements for ash lum- 
ber for use in the construction of airplanes. 

Materials 

2. Species. The following species of ash may be supplied: 

White ash Fraxinus americana 

Green ash Fraxinus lanceolata 

Blue ash Fraxinus quadrangulata 

Biltmore ash Fraxinus biltmoreana 

3. Grades. There shall be four grades of material as follows : 
Grade A. To be 18 feet and over long, 6 inches or wider, 

2 to 4 inches thick. Pieces 8 to 12 feet surface measure may 
have one sound, tight knot 1J inches in diameter or its 
equivalent. Pieces over 12 feet may have two such knots or 
the equivalent. The general direction of the grain shall not 
deviate from the longitudinal axis of the piece at a greater 
angle than 1 in 15. 

Grade B. To conform to general rules for grade A and to 
be 14 to 17 feet long, 6 inches or wider, and li inches in thick- 
ness. 

Grade C. To conform to general rules for grade A and to 
be 8 to 13 feet long, 6 inches or wider, and 1 to 4 inches in 
thickness. 

Longeron stock: To be practically clear of all defects. 
Pieces 8 to 12 feet surface measure may have one sound, 
tight knot | inch in diameter or its equivalent. Pieces 12 to 
16 feet surface measure may have two such knots or the equi- 
valent, and pieces having over 16 feet surface measure may 
have three or the equivalent. The general direction of the 



WOODS USED IN CONSTRUCTION 



81 



grain shall not deviate from the longitudinal axis of the piece 
at a greater angle than 1 in 20. 

Quality 

4. All lumber shall be manufactured from live, healthy 
trees. No material to be accepted which is known as pump- 
kin ash or which is cut from swell butt and bottle neck por- 
tions of swamp-grown ash. Material shall be free from decay, 
worm holes, doty wood, unsound or loose knots. 

5. Defects. Equivalent defects to be used in grading 
lumber. 



NUMBER 


SOUND AND 
TIGHT KNOTS 


SOUND AND 
ENCASED KNOTS 


THROUGH CHECK 
AND SPLIT 


SURFACE 
CHECKS 


Average 
diameter 


Average 
diameter 


Length 


Width and 
length 


1 

2 
4 

8 


inches 

n 

i 

5 

8 

8 


inches 
1 

5 
8 
3 
8 
1 
4 


inches 

8 
5 
3 

2 


inches 

1*6x16 
&xl2 

^x 9 



Figures on horizontal lines represent equivalent, and the 
number of defects refer to the number of smaller defects that 
are equivalent to the larger ones of the same or different kinds. 

Manufacture 

6. Measurement. In the measurement of lumber of 
random widths, fractions of over \ foot, as shown on the 
board rule, must be counted into the next higher figure; 
fractions of exactly \ foot and less must be counted back 
to the next lower figure. 

7. Dimensions. All lumber shall be sawed square edge 
and full to sizes given. Ninety per cent of the minimum widths 
mentioned in all grades of lumber must be full width, the 



82 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



remaining 10 per cent may be \ inch scant in width. The 
following allowance will be made for finish in seasoned 
lumber: 



GREEN (ROUGH SAWED.) 


ALLOWANCE FOR FINISHING 




SIS 


S2S 


Thickness : 

1| inches or under 


inches 

l 

8 
3 

16 


inches 

3 


If inches to 4 inches 


l 







8. Tally. A piece tally in feet must be made of all 
material. All lumber 1 inch or less in thickness shall be 
counted face measure. To obtain the board measure of 
lumber thicker than 1 inch the face measure must be multi- 
plied by the thickness expressed in inches and fractions of 
inches. 

9. Stain. Stain that will surface off in dressing to stand- 
ard thickness will not be considered a defect. 

10. Wane. In the grades A, B, and C, wane along the 
edge not exceeding one-sixth the length of the piece, or its 
equivalent at one end or both ends, not exceeding in thick- 
ness one-half the thickness of the piece and not exceeding J 
inch in width in 1-inch to 2-inch lumber or 1 inch in width 
in 2|-inch and thicker lumber, will not be considered a 
defect. 

Inspection 

11. All material shall, before acceptance, be inspected in 
accordance with the general specifications for inspection of 
material referred to in paragraph 1. 

12. Inspection to be at point of manufacture unless other- 
wise specified. The inspector shall have free access to all 
parts of the mills where the lumber is being manufactured 



WOODS USED IN CONSTRUCTION 83 

and shall be afforded every facility to satisfy himself that 
the lumber conforms to this specification. 

13. The inspector shall stamp each piece of accepted lum- 
ber with the official acceptance stamp. 

Shipment 

14. Rail shipments shall be made in closed cars, protected 
from the weather. The lumber must be carefully piled to 
avoid damage in transit. 

WHITE PINE, SUGAR PINE, AND WESTERN WHITE PINE FOR 
AIRCRAFT CONSTRUCTION 

General 

1. White pine (Pinus strobus), sugar pine (Pinus lamber- 
tiana), and western white pine (Pinus monticola) used for 
aircraft construction shall be sound, free from wormholes, 
shake, rot, brashiness, loose knots, and injurious irregular 
grain. 

2. Ten per cent of the pieces in a shipment may include a 
few scattered pin knots and pitch pockets not over 2 inches 
in length. 

3. Bright sap will be allowed. Slight blue stain will not 
be considered a defect. 

4. All lumber to be cut from live and healthy trees. 

5. Limits for the slope of cross or spiral grain shall not 
exceed an angle of more than 1 in 20. 

6. The minimum specific gravity of eastern white pine 
and sugar pine based on volume and weight when oven-dry 
shall be 0.36 and of western white pine 0.40. 

Q. What is moisture content? 

A. All green or partially dried wood contains a certain 



84 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

percentage of moisture or water. A portion of this water 
is known as free water. The other water or moisture con- 
tained in woods is that retained in what is known as the 
hygroscopic cells and the fiber saturation point is known when 
the moisture content of a tested specimen shows 25 per cent. 
This is the point at which the moisture contained in the 
hygroscopic cells begins to evaporate. 

Q. How much moisture content is there in green lumber? 

A. Green lumber may contain from about one-third to 
two and one-half times its oven-dry weight of water. Ex- 
pressed in percentage, there is from 33| to 250 percentage of 
moisture based on the oven dry weight. 

Q. How many methods are there of drying lumber? 

A. Two, one being known as air drying and the other as 
kiln drying, kiln drying being used almost exclusively for 
material to be used in aircraft construction. 

Q. What is a dry kiln? 

A . There are two kinds of dry kilns, one being stationary 
and the other portable. The stationary dry kiln usually 
consists of a brick or wooden enclosure, rectangular in shape, 
with steam radiators on one side and cold water radiators on 
the opposite side; also equipped for ejecting live steam in 
same in order to raise the humidity. Tracks are provided 
upon which trucks containing the material to be dried is 
properly spaced in order that the heated air can circulate 
through same. It is absolutely essential that the heat 
thrown off by the steam radiators should circulate and the 
cold water passing through the radiators on the opposite 
side of the enclosure draws the heated air towards it, there- 
fore, setting up the necessary circulation. All dry kilns 
should contain several thermometers in addition to a com- 



WOODS USED IN CONSTRUCTION 85 

bined thermometer and hydrometer, both recording and 
nonrecording in order that the temperature and humidity 
may be known and governed throughout the charge. 

A kiln known as the cutler dry-kiln was used extensively 
by various firms in kiln-drying aircraft material. This con- 
sists of a temporary frame work installed in various parts 
of a plant, being canvas covered, usually rectangular in 
section with steam radiators such as used in heating buildings, 
etc., with steam pipe running over the top of radiators par- 
allel to same upon which several petcocks are installed in 
order to turn five steam in the enclosure to raise the humidity. 

Opposite these radiators is a row of electric fans arranged 
to blow against the radiators at an angle of 45 degrees. This 
causes the heated air to strike the side of the enclosure, which 
is reflected backwards and passes over the charge of material 
in the kiln and returns by passing through the spaces be- 
tween the material et cetera, thereby setting up the necessary 
circulation for even drying throughout. 

Two steps are necessary in the drying of lumber: first, the 
evaporation of moisture from the surface, second, the passage 
of moisture from the interior to the surface. Heat hastens 
both of these processes. For quick drying, as high a tem- 
perature should be maintained in the kiln as the wood will 
endure without injury. Dry hot air will evaporate the mois- 
ture from the surface more rapidly than it can pass from the 
interior to the surface, thus producing uneven drying, with 
consequent damaging results. To prevent excessive evapor- 
ation, and at the same time keep the lumber heated through, 
the air circulating through the piles must not be too dry; 
that is, it must have a certain humidity. 

Humidity is of prime importance, because the rate of 
drying and the prevention of checking and case hardening 
are directly dependent thereon. Only one species and 
approximately one thickness should constitute a kiln charge. 



86 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



A difference not to exceed \ inch in thickness should be 
allowed. 

The following is a brief description of the process of kiln 
drying from start to finish: First, a test should be made of 
the stock to be dried to determine the moisture content. 
This is done by weighing a few samples taken from the 
material and then placing samples in an electric oven and 
under a temperature of 212° F. until the material is bone-dry, 
when a difference in weight will determine the moisture 
content. Green wood as well as previously air dried wood 
after being placed in the kiln is steamed for a period of five 
to six hours for each inch of thickness and the humidity 
during this steaming period for either material must be 
either 100 per cent or not below 90 per cent in every portion 
of the pile. 

The following table gives the range of temperatures and 
humidity throughout the period of drying: 



STATE OF DHYING 



At the beginning 

After fiber saturation is passed (25 per cent) 

At 20 per cent moisture 

At 15 per cent moisture 

At 12 per cent moisture 

At 8 per cent moisture 

Final 



DRYING CONDITIONS 


Maximum 
tempera- 
ture 


Minimum 
relative 
humidity 


°F. 


per cent 


120 


80 


125 


■ 70 


128 


60 


138 


44 


142 


38 


145 


33 


145 


33 



It is to be noted that there are samples of this material 
placed in various parts of the pile in order that they can be 
readily removed so that the reduction in moisture content 
can be determined in order that the range temperature and 
humidity may be changed. 



WOODS USED IN CONSTRUCTION 87 

All aircraft material is dried down to a moisture content 
between 12 and 15 per cent, the idea being that the material 
should not contain more than 15 per cent moisture when 
placed in a machine. Material removed from a dry kiln 
before being tested should have from a week to ten days to 
adjust itself to shop temperature before being worked up. 

It is to be noted that it takes anywhere from eight to 
fourteen days to kiln dry material, the length of time depend- 
ing on the moisture content and the thickness of the material. 

Great care is always to be taken when material reaches the 
fiber saturation point, which is usually when the samples 
show 25 per cent moisture content, that the material does 
not become case hardened, thereby ruining the material, as 
very slight case hardening only is permissible. 

Before the material is removed from the kiln, in order to 
determine whether or not the material is case hardened, 
sections should be cut from the plank or timbers not nearer 
than two feet to the end of pieces. Samples shall then be 
sawed parallel to the wide face of the original board into 
tongues or prongs, leaving about one-half of the wood at one 
end of the section. If the prongs remain straight under a 
drying of twenty-four hours, perfect conditions of stress and 
moisture content are indicated. If the outer prongs bend 
in, conditions of case hardening are indicated. 

It is to be noted that kiln drying or air drying of wood in- 
creases its strength, but engineers in designing, where large 
timbers are used, do not figure on this increased strength as 
they use material which contains checks, therefore, it is not 
the factor to be used in that type of design. 

It is also to be noted that wood in drying does not decrease 
in cross section until the fiber saturation point is reached, 
which has been described in the foregoing. 

Material used for the manufacture of the propellers is 
dried until the moisture content is only 7 per cent. 



CHAPTER V 

Propeller Manufacture, Splices, Struts, Wood 
Protective Coatings 

Q. How is a propeller manufactured? 

A . Propellers are manufactured from three different kinds 
of wood, namely, mahogany, oak, and walnut. 

Laminations are sawn out from a template whose dimen- 
sions have been taken from the drawings. They are then 
given a surface drying in the kiln before being glued together, 
the laminations being marked to show how they should be 
glued. The temperature of the kiln, just previous to gluing 
the laminations for surfacing drying, should be 120° F., for 
thirty minutes to two hours with a humidity of 55°. They 
are then glued together, using certified hide or animal glue, 
and are to be kept in the clamps for 24 hours and after the 
removal of the clamps they should be allowed to set for an 
additional 24 hours, in the meantime being inspected for 
faulty joints, etc. 

The glue used for this purpose should be heated to a tem- 
perature of 140° to 150° F., and is mixed with water at the 
ratio of two and one-half parts of water by weight to one part 
of glue by weight. Precautions should be taken that only 
a sufficient quantity should be mixed for one day's work. 
The brushes and pots used should be cleaned at the close of 
working hours. Keep glue pot cover on during heating 
of glue to avoid evaporation of water in glue. Keep forms 
clean and free of glue, the temperature of the room while 
laminations are in clamps at 90° F., and while out of the 
clamp at 80° F. 

All laminations should be of vertical or quarter-sawed 

88 



PROPELLER MANUFACTURE 89 

grain or all flat grain if same is authorized, but vertical or 
quarter-sawed grain laminations should never be used to- 
gether. In applying glue, laminations are coated on the 
upper side of one piece and the lower side of the other. 

After laminations have been glued and inspected and found 
satisfactory, they are shaped either by machine or hand. 
The shaping of propeller blades by machine is usually done by 
an Ober lathe which uses a hardened master blade as a guide 
for roughing up. Where shaping is done by hand, draw 
knives and spoke shaves are used. In shaping out the pro- 
peller, a surface gauge is used, a protractor gauge graduating 
from one-tenth degrees, also a metal camber gauge. Pro- 
pellers are balanced before the hub hole is enlarged for 
installation of hub bushing. 

After propeller is balanced, the hole in the hub is enlarged, 
bushing pressed in with a neat fit, holes are bored and bolts 
pressed in two at a time by the use of an Arbor hand press. 

Propellers are given a coat of filler, rubbed down and 
polished with rottenstone and oil. Two coats of varnish 
are used, both coats being well rubbed in. 

Tips of all propellers are coppered on the leading edge for 
about 18 inches and on the trailing edge for about 6 inches. 
The place to receive the copper is first shaved off to a depth 
the thickness of the copper; 14 ounce copper is used for this 
work. Copper is first cut out to a template, then riveted in 
place with copper rivets, then soldered over the head of 
rivets, then surplus solder removed and polished and drill 
three small holes in the end of copper to let any moisture 
that may accrue escape. 

The propeller is balanced and, if not approved, a slight 
amount of material is removed in the vicinity of the hub in 
order to correct the balance. 

Some propellers, instead of being copper tipped, are covered 
with linen and doped. 



90 



AIRPLANES, AltlSHIPS, AIRCRAFT ENGINES 



Q. Is it permissible to splice wing spars? 
A. Yes. The length of the taper should be ten to one of 
the cross sections. See sketch with description below. 

^— Tape. \A/ft,fipirtc£ 

1^1 




«- 2' 



r*-k* 



% 



6 £qucA 5 paVei 



?kes -H *- 



Z"H 



y f~ TbpC \Nrappmdj 



tfordiMood J)o\r*el$. 




SOLID DIKY\ SPLICE. 

Q. What stresses come upon wing spars, ribs, et cetera, 
when aeroplane is in flight? 

A. The front spar is in tension and the rear spar is in 
compression, the ribs being in shear and bending. 

Q. What stresses come upon interplane struts, or wing 
posts, as they are sometimes called, in a biplane? 

A. These struts are always in compression, regardless 
of the position in which the aeroplane may be in at any time. 



Q. Of what material are interplane struts made? 

A. Struts are usually made of spruce, either from one 
solid piece or two or three laminations glued together with 
Casein glue, certified hide or animal glue. In large struts 
for heavy machines where three laminations may be used, 
the major portion of the center lamination may be hollowed 
out, except at the ends. 

Some struts are made of metal tubes and stream lined with 
spruce or other light material, being wrapped and then doped. 

Recent developments have shown that laminated struts 
that are wrapped with linen tape and doped do not stand up 



PROPELLER MANUFACTURE 



91 



well, as moisture gets in between the tape and wood causing 
the glue to soften and laminations come apart. Solid or 
laminated struts shall not be fabric covered. 

The very latest method to keep out moisture on both pro- 
pellers and struts where struts are built up of laminations — 
is to coat the surface with size, and then apply aluminum 
leaf which comes in booklet form, similar to gold leaf. After 
the application of aluminum leaf, and in order to make the 
surface uniform throughout, powdered aluminum is applied 
by the means of padded cotton. 

It is to be noted that where any parts of aircraft material 
are to be spliced, such as longerons or wing beams, that just 
previous to applying the glue, a hot iron, usually an electric 
iron should be applied to the surfaces to be glued in order to 
remove any surface moisture. 

WOOD PROTECTIVE COATINGS 

The best protective coatings for wood parts used in air- 
craft construction is spar varnish. 

The following table shows the resistance of wood to mois- 
ture, that has been given one or more coats of varnish. 



NUMBER 
OF COATS 
OF SPAR 


PERCENTAGE OF MOISTURE 

EXCLUDED (BASED ON UNTREATED 

SPECIMENS) 


PERCENTAGE OF INCREASE 

IN WIDTH DUE TO ABSORPTION 

OF MOISTURE 


VARNISH 


First 
varnish 


Second 
varnish 


Third 
varnish 


First 
varnish 


Second 
varnish 


Third 
varnish 





0.0 


0.0 


0.0 


8.61 


8.61 


8.61 


2 


76.7 


72.0 


65.5 


2.01 


2.41 


2.97 


4 


86.2 


75.8 


76.9 


1.19 


2.08 


1.99 


6 


88.6 


81.7 


83.0 


0.98 


1.57 


1.46 


8 


91.0 


86.9 


86.2 


0.77 


1.30 


1.19 


10 


93.0 


88.4 


87.3 


0.60 


1.00 


1.09 


12 


94.3 


89.0 


87.2 


0.49 


0.90 


1.10 



92 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

All flying boats are given two coats of varnish on the in- 
terior, except in the cockpits where an overflow of gasoline, 
or from other causes that gasoline may come in contact with 
the woodwork, this being given two coats of shellac which is 
not soluble by gasoline. 

The side and top planking in H-S boats, being of only one 
thickness, is covered with fabric for water tightness. The 
planking is given a coat of marine glue. The fabric is then 
carefully placed on end caused to adhere firmly by being 
ironed with a hot iron. An electric iron is usually used for 
this purpose. This is followed by the application of one 
priming coat of naval gray enamel paint which has been 
thinned by adding one quart of turpentine to a gallon of the 
above paint. This is followed by two coats of the standard 
naval gray enamel. The exterior of bottom is given a coat 
of filler varnish, followed by two coats of naval gray enamel 
paint. 



CHAPTER VI 

Aircraft Wires and Their Uses 

Q. How many kinds of wire are used in the construction 
of aircraft? 
A. Four kinds, as follows: 

(1) Aircraft Wire, is composed of one solid wire, 

tinned, and of round section. 

(2) Aircraft Strand — non flexible — 19 strand gal- 

vanized. 

(3) Aircraft Cable or Cord, flexible galvanized 7 

strands of 7 wires each. 

(4) Aircraft Cable or Cord, extra flexible, tinned 7 

strands of 19 wires each. 

Q. Which is the strongest of the four wires when each are 
of the same diameter? 

A. The breaking strength of the above wires are in the 
following order: Solid wire, strand wire, extra flexible, flex- 
ible, the solid wire being the strongest. 

Tables 1, 2, 3 and 4 give complete information on the 
size, weight, and breaking strengths of the above mentioned 
wires. 

Q. Where are the various wires mentioned used on air- 
craft? 

A. Solid tinned wire is used for all diagonal and cross 
bracing of a fuselage of the N-9 type seaplane in bracing 
all sections of fuselage in the rear of the rear pilot's cockpit, 
for bracing control horns, on ailerons, elevators, rudders, all 

93 



94 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



Table 1 
Tinned aircraft wire 



AMERI- 
CAN 
WIRE 
GAUGE 


DIAMETER 


WEIGHT 

PER 100 

FEET 


BREAK- 
ING 
STRENGTH 


AMERI- 
CAN 
WIRE 
GAUGE 


DIAMETER 


WEIGHT 

PER 100 

FEET 


BREAK- 
ING 
STRENGTH 




inches 








inches 









0.325 


28.16 


15,000 


11 


0.091 


2.20 


1,620 


1 


0.289 


22.27 


12,500 


12 


0.081 


1.744 


1,300 


2 


0.258 


17.75 


10,400 


13 


0.072 


1.383 


1,040 


3 


0.229 


13.97 


8,300 


14 


0.064 


1.097 


830 


4 


0.204 


11.10 


6,700 


15 


0.057 


0.870 


660 


5 


0.182 


8.84 


5,500 


16 


0.051 


0.690 


540 


6 


0.162 


7.01 


4,500 


17 


0.045 


0.547 


425 


7 


0.144 


5.56 


3,700 


18 


0.040 


0.434 


340 


8 


0.128 


4.40 


3,000 


19 


0.036 


0.344 


280 


9 


0.114 


3.50 


2,500 


20 


0.032 


0.273 


225 


10 


0.102 


2.77 


2,000 


21 


0.028 


0.216 


175 



Table 2 
Galvanized non-flexible — 19 strand 



DIAMETER 


WEIGHT PER 100 FEET 


BREAKING STRENGTH 


inches 








0.312 = 


A 


20.65 


12,500 


0.250 = 


1 

4 


13.50 


8,000 


0.218 = 


7 
32 


10.00 


6,100 


0.187 = 


3 
T6 


7.70 


4,600 


0.156 = 


5 
32 


5.50 


3,200 


0.125 = 


1 
8 


3.50 


2,100 


0.109 = 


A 


2.60 


1,600 


0.094 = 


3 

32 


1.75 


1,100 


0.780 = 


A 


1.21 


780 


0.062 = 


A 


0.78 


500 


0.031 = 


i 

32 


0.30 


185 



AIRCRAFT WIRES 



95 



Table 3 
Galvanized-flexible — cable (7 strands of 7 wires each) 1x7 



DIAMETER 


WEIGHT PER 100 FEET 


BREAKING STRENGTH 


inches 






0.312 = A 


16.70 


9,200 


0.250 = I 


10.50 


5,800 


0.218 = 3 V 


8.30 


4,600 


0.187 = T 3 e 


5.80 


3,200 


0.156 = A 


4.67 


2,600 


0.125 = | 


2.45 


1,350 


0.094 = A 


1.45 


920 


0.078 = & 


0.93 


550 


0.062 = T V . 


0.81 


485 



Table 4 
Tinned — extra flexible — cable (7 strands of 19 wires each) 7 x 19 



DIAMETER 


WEIGHT PER 100 FEET 


BREAKING STRENGTH 


inches 






0.375 = | 


26.45 


14,400 


0.344 = M 


22.53 


12,500 


0.312 = tV 


17.71 


9,800 


0.281 = a 9 2 


14.56 


8,000 


0.250 = I 


12.00 


7,000 


0.218 = -h 


9.50 


5,600 


0.187 = t\ 


6.47 


4,200 


0.156 = 3 5 2 


4.44 


2,800 


0.125 = \ 


2.88 


2,000 



Note: If wires are galvanized instead of tinned the strengths 
-ill be about 10 per cent less. 



internal wires of wings and non-skids, also for bracing wing 
tip floats on N-9 type seaplanes. 

Strand wire is used to brace an N-9 fuselage forward of 
the rear cockpit and engine section, load and lift wires, pon- 
toon float brace wires. 



96 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Flexible is not used to any great extent now, but when used 
it is for control wires where a certain amount of flexibility 
is required, but not around pulleys. 

Extra flexible cable is used for control wires exclusively, 
and when used in conjunction with flexible cable — the extra 
iexible being always used around pulleys. 

Q. In view of solid wire being stronger than the other 
wires of the same diameter, why is it not used elsewhere on 
aircraft? 

A. The reason is, that excessive vibration causes solid 
wire to become fatigued, or crystallized, and it would soon 
break; such as is produced in the forward cockpits and engine 
section of a fuselage or load and lift wires, and on account of 
its stiffness could not be used for control purposes. 

Q. On what wires are thimbles used in making up their 
terminals? 

A. On all 19 strand, flexible and extra flexible wire. 

Q. Are terminals in flexible and extra flexible and 19 
strand wire on account of using thimbles made alike? 

A. No. The terminals of flexible and extra flexible wires 
are made by splicing an eye around a thimble, the kind of 
splice being known as the navy terminal splice. 19 Strand 
wrapped described on page 100. 

Q. How is the navy terminal splice made, and how is a 
terminal made in control wires? 

A . This terminal is known as the navy splice terminal and 
shall be used exclusively on 7 by 19 extra flexible steel cable 
controls and 7 by 7 flexible steel cable. It may also be used 
for fiber and rope cord splicing. 



AIRCRAFT WIRES 97 

Serving Cord: The serving cord shall be a seven-strand 
linen machine cord or an equivalent cotton cord, and after 
serving given a coat of shellac. 

Cutting: Before the cable is cut it shall be thoroughly 
soldered for 2 or 3 inches to prevent any slipping of the wires 
after cutting. The flux used in this soldering shall be stearic 
acid rosin. Sal ammoniac or other compounds having a cor- 
rosive effect will not be permitted either as a flux or for 
cleaning the soldering tools. The cable shall be cut to the 
proper length bj^ mechanical means only. The use of oxy- 
acetylene torches in any manner is not permitted. 

Forming: The cable is bent securely around the proper 
size thimble and clamped, the tip of the thimble having pre- 
viously been bent back to permit a tight splice. The length 
of the free end of the cable from point of thimble should be 
2 to 3 inches longer than required to produce the number of 
tucks called for in table 1. 

Splicing: After the cable is securely clamped in the thimble 
the strands are to be broken apart where soldered at the ends 
and separated back to the point of thimble. The number 
of tucks called for in the various sizes of cable is shown in 
the accompanying table 1. 

A small wood, fiber, or copper mallet shall be used in 
pounding the splice. The anvil on which the splice is 
pounded shall be made of hardwood. 

The process of making the splice is as follows: Take first 
free strand on right-hand side and tuck it under first strand 
which is nearest the point of the thimble on the right. Take 
free strand directly underneath the first strand and tuck it 
through the center of the cable. Three longitudinal strands 
should then lay each side of this tucked strand. Then insert 
the core wire directly over the same strand so that these two 
strands will come out in the same position. Then take the 
free strand on the extreme left and tuck it underneath the 



98 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

strand which is nearest the point of the thimble on the left. 
Then take the free strand which runs parallel to the first 
free strand on the right side and tuck it under the longi- 
tudinal strand which is directly above the first longitudinal 
strand which had been tucked. Five strands should now 
have been tucked and two remain free. Then take the free 
strand on the left and tuck it toward the right underneath 
the remaining longitudinal strand. This free strand must 
come out directly above the second free strand which had 
been tucked. Then take the remaining free strand which is 
located on the right and tuck it toward the left underneath 
the same longitudinal strand. At this point a free strand 
will be between each longitudinal strand with the exception 
of the core wire which comes out with the center strand. 
The whole of the above is called the first tuck. At this point 
two free strands which cross directly above one another at 
the eye will be prominent. These strands should be pounded 
down to tighten the splice to the thimble. 

For the second tuck, take the free strand on the opposite 
side of the splice which comes out to the right of the core 
strand and tuck it to the left over longitudinal strand and 
underneath the next longitudinal strand. This binds in the 
core strand to center of the splice. Repeat this operation 
with all the remaining free strands to the left. The tucks 
should now be again pounded down to make the splice tight 
and symmetrical. For the third tuck, take the strand which 
comes out to the right of the core strand and tuck it toward 
the left over the first longitudinal strand and under the next 
longitudinal strand. This operation will bind in the core 
strand. Repeat this operation with all the remaining free 
strands to the left. The core wire is then cut off close to the 
splice and the tucks are pounded as previously directed to 
tighten splice and to make it symmetrical. All free strands 
are now reduced one-third, but should not be cut until the 



AIRCRAFT WIRES 



99 



following complete tuck has been, made by the six remaining 
two-thirds strands as heretofore directed for the full strand. 
This completes the fourth tuck. The free untucked one- 
third strands should now be cut off close to the splice. The 
sphce is again pounded as previously directed. The free 
strands should now be halved and tucked to the left, allow- 
ing the remaining one-third strands to be free as previously 
indicated. The six remaining one-third strands are then cut 
off close to the sphce. Cable one-fourth inch in diameter 
and larger should be spliced with six tucks in place of five to 
insure strength and proportion. In this case four complete 
tucks are made in place of three before starting to taper, as 
shown in table 1 

Serriug: P'ace the end of the serving cord on the cable 
one-fourth inch above the fifth tuck. Carry the cord on the 
cable toward the thimble to a point midway between the 
thimble and the third tuck. From this point the cord should 

Table 1 






DTAMETER 


7 BT 19 TINNED 
CABLE 


7 BY 7 GALVANIZED 
CABLE 


NUMBER OP TUCKS 


OF 
CABLE 


Breaking 
strength 


Proving 
load* 


Breaking 
strength 


Proving 
load* 


Pull . 
strand 


Two- 
thirds 
strand 


One-third 
strand 


inches 


pounds 


-pounds 


pounds 


pounds 








3 

32 


800 


480 


920 


552 


3 






1 

8 


2,000 


1,200 


1,350 


810 


3 






¥2 


2,800 


1,680 


2,600 


1,560 


3 






Tg 


4,200 


2,520 


3,200 


1,920 


3 






3 7 2 


5,600 


3,360 


4,600 


2,760 


3 






1 
4 


7,000 


4,200 


5,800 


3,480 


4 






f~s 


8,000 


4,800 


7,200 


4,320 


4 






T77 


9,800 


5,880 


9,200 


5,520 


4 






XI 


12,500 


7,500 






4 






8 


14,400 


8,640 


11,900 


7,145 


4 







* Proving load is 60 per cent of the breaking strength. 



100 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

then be tightly and closely served around the cable, covering 
all tucks to a distance on the unspliced portion equal to the 
diameter of the wire. The cord is then snubbed by inserting 
the end under four convolutions of the serving and the con- 
volutions drawn tightly down on the cable. The serving is 
to be given two generous coats of shellac. 

Proving: All tension and control cables shall be subjected 
to the proving load shown in table 1 under the heading 
"Proving." The load shall be applied gradually, taking ap- 
proximately three seconds and maintained for a period of not 
less than one-half a minute. The proving load is estimated 
at 60 per cent of the breaking strength of the cable. The 
proving load takes out much of the stretch of the cable and 
splice and allows the total take-up of the turnbuckle to be 
more effective. 

Q. How is a terminal made in 19 strand galvanized wire 
cable? 

A. (1) Use a flux composed of stearic acid and rosin, 
stearic acid 25 to 50 percent, rosin 75 to 50 percent, using a 
warming glue pot to keep the flux in a fluid state. 

(2) Cutting. Before cutting the cable the wires must be 
soldered or welded together to prevent slipping. The pref- 
erable process is to thoroughly tin and solder the cable for 
2 or 3 inches by placing in a solder trough, finishing smooth 
with soldering tool. The cable may be cut diagonally to 
conform to the required taper finish. 

(3) Forming. After soldering and cutting, the cable is 
securely bent around the proper size thimble and clamped, 
taking care that the cables lie close and flat and that the 
taper end for finish lies on the outside. If it is necessary to 
trim the taper at this point in the process, it is preferable that 
it be done by nipping, but grinding will be permitted pro- 
vided a steel guard at least 3 inches long and jj inch thick 



AIRCRAFT WIRES 101 

be placed between the taper end and the main cable during 
the operation and that the heat generated from the grinding 
does not melt the solder and loosen the wires. 

(4) Serving. Serving may be done by hand or machine, 
but in either case each serving convolution must touch the 
adjoining one and be pulled tightly against the cable, with 
spaces for permitting a free flow of solder and inspection. 

(5) Soldering. Care must be exercised to prevent draw- 
ing of the temper of any cable wires by excessive temperature 
or duration of applied heat. The flux used in this soldering 
shall be stearic acid and rosin as called for in paragraph (1). 
Sal ammoniac or other compounds having a corrosive effect 
will not be permitted either as a flux or for cleaning the sol- 
dering tools. 

(6) Soldering is accomplished by immersing the terminal 
alternately in the flux and in the solder bath, repeating the 
operation until thoroughly tinning and filling with solder 
under the serving wire and thimble is obtained. The tem- 
perature of the solder bath and place where terminal is with- 
drawn shall not be above 450°F. A soldering iron may be 
used in the final operation to give a secure and good appearing 
terminal. Care must be taken that the solder completely 
fills the space under the serving wire and thimble. A slightly 
hollowed cast-iron block to support the splice during solder- 
ing may help in securing best results. Abrasive wheels or 
files for removing excess solder will not be permitted. 

(7) As an alternative process of making terminals for 
non-flexible cable, the oxyacetylene cutting method and the 
presoldering method (soldering before wrapping) are per- 
mitted, but only on the following conditions: (1) That the 
process of cutting securely welds all wires together; (2) That 
the annealing of the cable does not extend more than one 
cable diameter from the end; (3) That no filing be permitted 
either before or after soldering: (4) For protection during the 



102 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



operation of grinding the tapered end of the cable, a steel 
guard at least 3 inches in length and -^ inch thick, shall be 
placed between the taper and the main cable; (5) The heat 
from grinding shall not draw the temper of the cable. 

(8) Proving. All cable terminals shall be subjected to the 
proving load. The proving load shall be applied gradually, 
taking approximately three seconds and maintained for a 
period of not less than one-half minute. The means of ap- 
plying the proving load shall be such that the specified load, 
for each size of cable, can not be exceeded through careless- 
ness on the part of the workman. The proving load is esti- 
mated at 60 per cent of the breaking strength of the cable and 
takes out much of the stretch of the terminal, allowing the 
total take-up of the turnbuckle to be more effective. 

(9) Serving wire. The serving or wrapping wire shall be of 
soft annealed steel wire thoroughly and smoothly tinned or 
galvanized, the diameter of the wire used for wrapping to be 
in accordance with the following table: 

Table of Dimensions in Inches 



CABLE 


TERMINAL DIMENSIONS 


Diameter 
of cable 


Breaking 
strength 


Proving 
load 


L. 


D. 


c. 


Serving 

wireB. & S. 

gauge 




pounds 


pounds 










A 


500 


300 


2 


A 


I 


24 


3 


1,100 


700 


21 


3 

4 


I 


24 


I 


2,100 


1,200 


21 


7 

8 


i 

8 


24 


5 


3,200 


1,900 


3i 




1 
8 


24 


A 


4,600 


2,800 


3| 


-1 1 
x 8 


1 
8 


20 


A 


6,100 


3,600 


4 


1 1 

x 4= 


1 

8 


20 


1 

4 


8,000 


4,800 


41 


1 3 
^8 


TS 


20 


A 


12,500 


7,500 


5i 


1 5 
x 8 


T6 


20 


3 

8 


17,500 


10,500 


6i 


1 *4 


1 

4 


18 


7 
16 


23,500 


14,000 


7 


2i6 


1 
4 


18 


1 
2 


28,500 


17,000 


8 


2h 


1 
4 


18 



AIRCRAFT WIRES 103 

TERMINAL FOR SOLID WIRE, ROUND SECTION 

The terminal loop is preferably formed in a bending ma- 
chine, the ferrule being slipped over wire after loop is formed, 
and slipped tightly in position, the free end of wire then being 
bent snugly over the ferrule, the free end then being cut off 
so that it will cover from 3 to 5 turns of ferrule; the ferrule 
being made of 8 turns of wire of a similar gauge as the wire 
itself. 

The soldering is accomplished by immersing the terminal 
alternately in stearic acid and rosin flux and solder bath, 
repeating the operation until tinning and filling under the 
ferrule is accomplished. If it is impractical to solder termi- 
nal by the bath process, the entire soldering may be done with 
a soldering iron. Abrasive wheels or files should never be 
used for removing excess solder. These wires should be sub- 
jected to proving load equal to 60 percent of its breaking 
strength in order to take out the stretch of the loop and 
allow the turnbuckle take-up to be more effective. 

RIGID TERMINALS FOR STREAM LINE OR SWAGED WIRE 

The terminals shall be machined preferably from heat- 
treated, cold drawn or cold rolled bars. If terminals are not 
made from the above, they must be heat treated after ma- 
chining to give the necessary physical properties. 

ROUND SWAGED WIRE STAY RODS 

These wires are for use in aircraft where not exposed, such 
as inside of wings or fuselage, where greater strength is re- 
quired than is obtained through the use of solid tinned wire 
of round section, and are adjustable to tension through right 
and left screw threads on ends or shanks of rods which may 
be in the form of an eye or fork which has a hollow shank 



104 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

threaded to receive ends of rods. Are used principally on 
heavier type of aircraft. 

In connection with wires and their uses, it is to be noted 
that sometimes either 19 strand wire or solid wire tinned is 
used for the rudder controls — H-16's have solid wire and 
H-S-l's 19 strand wire, but neither is ever used around 
pulleys. 



CHAPTER VII 

TUENBUCKLES 

Q. What is a turnbuckle, and for what purpose is it used? 

A . A turnbuckle as used in aircraft construction consists 
of three parts, one being known as the barrel, another as the 
fork, and the other as the eye, the barrel being bored out 
hollow and threaded with left hand threads in one end and 
right hand threads in the other; the forks and eyes are gen- 
erally spoken of as turnbuckle shanks, one end of the fork 
or eye is threaded to screw into the barrel. 

Turnbuckles are used to put a tension on the various wires 
used in the assembly of the various aircraft units, etc. 

Q. Of what materials are the three parts composing a 
turnbuckle made? 

A. The barrels are made of high strength brass, being 
machined to size from bars of brass, with a tensile strength 
per square inch of 67,000 pounds. 

The shanks are made of nickel steel with a tensile strength 
of 125,000 pounds per square inch, being heat treated either 
before or after machining to refine the structure; these shanks 
are then zinc coated with a thickness of zinc approximately 
0.001 inch thick. 

Q. Are all turnbuckles of the same length that are used 
to tighten the same diameter wire? 

A. No. There are two lengths of turnbuckles used on 
the same size diameter wires. 

A short barrel turnbuckle is used on short wires and a long 
barrel turnbuckle is used on long wires, as there is not as 
much take-up in a short wire as there is in a long wire. 

105 



106 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



Q. How is the size of a turnbuckle determined? 
A. The size of a turnbuckle is determined by the diam- 
eter of the shanks. 

The following table gives complete information on turn- 
buckles. 







LENGTH 






PIN HOLES IN 


a 










TAKE 






o 


NAVY NUMBER 












z 




Threads 


Barrel 


Open 
CtoC 




Eye 


Fork 


K 
Eh 
DO 






inches 


inches 




inches 


inches 


pounds 


8-SEF 


6-40 


2.25 


4.5 


1.25 


t\ 


3 
16 


800 


16-SEF 


10-32 


2.25 


4.5 


1.04 


7 
32 


3 


1,600 


16-LEF 


10-32 


4.00 


8.0 


2.79 


& 


T 3 6 


1,600 


21-SEF 


12-28 


2.25 


4.5 


1.00 


3*2 


3 

16 


2,100 


21-LEF 


12-28 


4.00 


8.0 


2.75 


7 
32 


3 

16 


2,100 


32-SEF 


1-28 


2.25 


4.5 


0.61 


A 


1 
4 


3,200 


32-LEF 


1-28 


4.00 


8.0 


2.36 


9 
F2 


1 


3,200 


46-SEF 


^-24 


2.25 


4.5 


0.60 


5 
16 


5 
16 


4,600 


46-LEF 


A-24 


4.00 


8.0 


2.35 


5 
16 


5 
16 


4,600 


61-LEF 


1-24 


4.00 


8.0 


2.08 


M 


3 

8 


6,100 


80-LEF 


f-24 


4.00 


8.0 


1.81 


■§■ 


3 

8 


8,000 


125-LEF 


tV20 


4.25 


9.0 


2.06 


16 
32 


T ? 6 


12,500 


175-LEF 


1-20 


4.25 


9.5 


2.06 


1 9 6 


1 
2 


17,500 



Note: In column headed "Navy Number," the letters indicate 
the type of turnbuckle : S — Short, L — Long, E — Eye, F — Fork. Thus 
SEF indicates a turnbuckle having a short barrel, with one eye end 
and one fork end. 



The following is a table giving size, etc., of shackles used 
in connecting up wires in aircraft construction. It is to be 
noted that a turnbuckle contains three parts, previously de- 
scribed, but in very large turnbuckles the fork is omitted and 
another eye screwed into turnbuckle barrel. Where this is 
done, the turnbuckle consists of two eyes and barrel, the 
connection being made to the fitting by means of shackle 
being passed through eye of turnbuckle and then secured to 



TURNBUCKLES 



107 



fitting by a clevis pin; such clevis pins being secured by cotter 
or split pins as they are sometimes called. 



Shackles 



XI MBER 


DIAMETER 
OF WIRE 


DIAMETER 

OF 
PIN HOLE 


BETWEEN 
JAWS 


DIAMETER 
OF LOOP 


CENTER OF 

EYE TO 

CENTER OF 

LOOP 


STRENGTH 

SHACKLE 

AND CABLE 














pounds 


8 


0.172 


0.188 


0.109 


0.250 


0.563 


800 


16 


0.172 


0.188 


0.156 


0.250 


0.563 


1,600 


21 


0.172 


0.188 


0.156 


0.250 


0.563 


2,100 


32 


0.250 


0.250 


0.203 


0.375 , 


0.750 


3,200 


46 


0.281 


0.313 


0.203 


0.438 


0.813 


4,600 


61 


0.313 


0.375 


0.203 


0.500 


0.875 


6,100 



Clevis pins 

Note: The pins used with shackles, turnbuckles, stay-wire fit- 
tings and other airplane parts requiring ready assembly are called 
"Clevis pins" in these specifications. 

Those used with shackles and turnbuckles are supposed to be 
0.002 inch less in diameter than the pin hole. 

The following defects are frequently found in turnbuckles 
upon inspection at manufacturers: 

Barrels drilled eccentric with outside diameter. 

Mutilated shanks, deep tool marks, warped or bent steel 
shanks caused by rough handling or heat treatment. 

Cracked barrels, developed in machining. 

Shanks should screw into barrel with a snug true fit, 
and capable of being turned by hand to within J inch of fillet. 
Assembled turnbuckles should not show any appreciable side 
shake when three threads on shank are exposed. 



CHAPTER VIII 

Aircraft Fittings 
manufacture, welding, brazing 

Q. Of what material are aircraft fittings made? 

A . Aircraft fittings are made of both nickel steel and mild 
steel, except pulleys, which are made of high strength brass, 
Tobin bronze, or canvas bakelite. 

Q. How many methods are there used in making metal 
fittings? 

A. Four methods, as follows: Drop forging, stamping 
machines, by the use of chopping machines for cutting to 
shape and bending and finishing by hand, and castings used 
occasionally. Some fittings are cast, such as rudder bar 
supports, pontoon step castings, etc. 

Q. Name some fittings that are made by the above men- 
tioned processes? 

A. Turnbuckle shanks, sockets, brace ends, upper and 
under side wing plates, shackles, the lug end of a strut fitting; 
pontoon fittings are drop forged, the strut fittings in most 
cases and pontoon fittings in all cases having an additional 
part welded thereto to complete same. Numerous fuselage 
fittings and hinge parts are stamped out, and parts built up 
by welding or brazing together. Miscellaneous parts that 
it is not practical to manufacture by the above two methods 
are outlined on a sheet of steel by the means of scribe or light 
center punch marks and then chopped out to shape by a 
chopping machine which cuts about \ inch of metal along the 

108 



AIRCRAFT FITTINGS 109 

desired line at each stroke and operates very rapidly in an 
up and down motion. The nose plates for fuselage type 
machines are made as follows: Nearly all nose plates are 
made up of two pieces riveted together, being first outlined 
on sheet of steel from which to be made, then chopped out 
on outline, followed by chopping out lightened holes, then 
plates are annealed, then flanged (for stiffness) by placing 
same between two metal forms and hammering flanges 
around edges and lightened holes, drill holes for the two parts 
that require riveting together, then rivet, sand blast to clean 
same, zinc coat and black enamel for rust proofing. 

Q. Why are fittings annealed? 

A. Annealing softens the metal, and relieves internal 
strains or any crystalization that has taken effect. 

Q. What does annealing consist of? 

A. The process consists of heating the metal to a tem- 
perature above the critical range, 50 to 200°F., or approxi- 
mately 1650°F., and allowing same to cool slowly through 
the critical range, sometimes being left in the furnace with 
the heat turned off, or placed on warm sheets of steel away 
from dampness or cold drafts. 

Q. What is meant by heat treatment of metals, and what 
are its effects on same? 

A . The heat treatment of aircraft parts consists of placing 
parts to be heat treated in a furnace, which may be either 
heated by coal, oil, gas, or electricity, at the present time the 
oil furnace being preferred. Attached to this furnace is an 
electric Pyrometer which shows the temperature on a gauge 
located several feet away from the furnace, the critical range 
being 1600° F.. to which the fittings are heated, then removed 
from furnace and quenched in a trough of crude oil. Replace 



110 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

fittings in furnace, reheat to 1100° F., and place same on 
floor (either metal or dry ground) away from cold drafts and 
dampness; this partially draws the temper, thus refining the 
structure of the metal and relieving any internal strains. 
The degrees in temperature as given above are not used al- 
ways; the latter may be as low as 600° F., depending on the 
degree of hardness desired. 

Q. How are steel or other metals tested for their physical 
properties? 

A. The testing of metals consists of pulling same apart 
in a test machine designed for the purpose, and while being 
pulled apart, the following physical properties are deter- 
mined: Elastic limit, elongation, ultimate strength, and 
yield point. The procedure is as follows: A sample of the 
metal is machined to a predetermined diameter for eight (8) 
inches in length, then the ends of the original size are secured 
in the jaws of the test machine and the machine started. To 
determine the elongation it is necessary to place two prick 
punch marks on the test piece four (4) diameters apart of the 
piece being tested; the change in length divided by original 
length is the percent of elongation. Elongation is usually 
expressed in percentage of 2 inches. 

The elastic limit of a piece of metal is the maximum strain 
it will withstand without producing a permanent set. 

The yield point takes place after a test piece of material 
has reached its elastic limit. 

Ultimate strength occurs after the metal begins to yield, 
the maximum number of pounds stress per square inch equals 
load in pounds as read on the beam divided by areas of cross 
section. 

Reduction of area is determined by measuring area before 
and after elongation. 



AIRCRAFT FITTIXGS 111 

v 

Q. How are metals analyzed to determine their compo- 
sition? 

A . Shavings or turnings from a sample are given a chem- 
ical analysis in order to determine its component parts, and 
from this analysis the quantities of such impurities as sul- 
phur, slag, silicon, etc.. are determined. 



Q. What does a microscopic examination show? 

A . The microscope shows the fine or coarse texture, fibers, 
etc. Photographs are also made of the machined end of a 
sample piece: these will show the defective component parts 
plainly. 

Q. How are steels welded? 

A. In welding steels no flux is used. The oxygen acety- 
lene flame is applied, using a small rod of Swedish iron to fill 
in; care must be taken not to burn the iron; welded parts are 
annealed to relieve the local strains. 

Q. What defects may be expected? 

A. Too much metal, poor workmanship, non-adherence 
of parts welded, also welded out of true position. 

Q. What defects may be expected in drop forgings? 

A. Laps and cold sheets, splits, cracks, burned metal, 
defects at bends, undersize, and improperly drilled holes as 
to size and alignment. 

Q. What defects ma} r be expected in stamped or hand- 
made fittings? 

A. The principal defects are cracks in bends, oversize 
holes, and non-alignment. 



112 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. What is spot welding? 

A. Spot welding in aircraft work consists of electric weld- 
ing in small spots to hold two parts together so they may be 
brazed or welded together. The operation consists of plac- 
ing the two parts to be tacked together between two elec- 
trodes allowing a high current to pass through them. Spot 
welding is not depended upon for strength on account of its 
uncertainty. Superficial inspection will not determine 
whether it is a good weld or not, and it would have to be torn 
apart to determine its strength. However, it is a good meth- 
od of securing two parts together to be held in position for a 
further operation. 

Q. How many methods are there for brazing? 

A. Three — open fire, pot brazing, and torch. 

Open fire brazing consists of an iron stand with fire brick 
placed on top. Two torches are placed at angles of about 45 
degrees; the torches burn oil or gas and operate under about 
8 pounds pressure. At the bottom of the brick enclosure is a 
recessed brick which contains the molten flux (borax); a 
graphite coating is applied to the metal in the vicinity of that 
part to be brazed to prevent brazing material from adhering, 
except where desired. First heat metal to a cherry red, care 
being taken not to burn, then baste part to be brazed with 
the molten flux and apply brazing wire to parts to be joined 
together; as soon as wire touches it melts and flows in the 
joints. Turn the tube or fitting as the case may be, and 
when all joints are filled, remove same, and place on floor to 
cool. 

Pot brazing is an identical arrangement as previously de- 
scribed. The flame from the two torches is applied against a 
pot of spelter to which a small per cent of borax has been 
added; the parts to be brazed are immersed in the molten 
metal, a graphite coating being applied in the vicinity of 



AIRCRAFT FITTINGS 113 

part to be brazed to prevent adherence of surplus metal. 
Torch brazing consists of heating the parts to be brazed to- 
gether by means of an oxygen acetylene torch and a wire of 
spelter. This method has been discontinued on account of 
the intense flame frequently burning the metal. In connec- 
tion with brazing and welding the following is to be noted : 
Laminated fittings of metal normally under stress, which are 
brazed or welded, shall in addition be thoroughly riveted, or 
otherwise secured in a satisfactory manner. Brazed or 
welded joints shall not be depended upon to transmit high 
tensile stresses. Welding or brazing shall be restricted to 
parts not otherwise possible of fabrication, and only in ap- 
proved locations. 

BRAZED JOINTS 

Steel best suited for brazing should be of low carbon, pre- 
ferably not higher than 0.50 per cent; sulphur (maximum), 
0.15 per cent; manganese (maximum), 0.90 per cent; phos- 
phorus (maximum), 0.10 per cent. Alloy steels are also suit- 
able for brazing, providing the above limits of carbon, sul- 
phur, phosphorus, and manganese are not exceeded. 

Any parts requiring a bend of more than 45 degrees over a 
diameter equal to or less than the thickness of the plate shall 
be normalized before bending, and if the part is highly 
strained it shall be made from a steel whose upper critical 
range does not exceed 1580° F., and shall be heat treated. 
Heat treating improves the brazed joint as well as the steel. 
If the design of a fitting to be brazed is such as to permit the 
use of a steel which has ample strength in its normalized con- 
dition and does not require heat treatment, the upper criti- 
cal temperature range of the steel is immaterial. 

Flux. Stearine, borax, or, preferably, boracic acid may 
be used. Ammonium chloride, zinc chloride, or similar 



114 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

salts having corrosive properties or acids, shall not be used 
in the flux. 

Brazing wire. Brazing wire will be used having the fol- 
lowing chemical contents: 

per cent 

Copper , 68 to 72 

Lead (maximum) 0. 30 

Iron (maximum) 0. 10 

Total impurities (maximum) 1 .25 

Zinc Remainder 

The melting point of the brazing wire varies from 1650° to 
1760° F., and begins to appreciably lose its strength at 
1600° F. 

Cleaning. All parts to be brazed shall be thoroughly 
cleaned by sand-blasting, or with emery cloth, to remove all 
oxide and grease. No filing or abrasive wheels will be per- 
mitted. The parts should be reasonably well fitted and se- 
cured in position by clamps or spot welding. Treatment 
with weak hydrofluoric acid of 5 to 10 per cent strength for a 
very short period (one-half minute) may follow the sand- 
blasting in order to remove any small particles of sand, so 
that the brazing process will be successful. Hydrofluoric 
acid is the only acid that will be permitted for this purpose. 
The parts treated shall immediately be cleansed to remove 
all acid. This may be accomplished by dipping into weak 
soda solution (8 pounds sal soda, or 4 pounds of soda ash, 
and 25 gallons of water) and then rinsing thoroughly with 
hot water. 

Heating., Care must be exercised in heating the parts to 
be brazed that the metal on both sides be sufficiently heated 
to relieve strains. 

The brazing flame shall be neutral (neither oxidizing nor 
reducing) , but may vary on the oxidizing side (blue flame) ; 
but must not vary on the reducing side (yellow flame). 



AIRCRAFT FITTINGS 115 

The steel must not be overheated. A temperature of 
1770° to 1800° F. (light yellow) should not be passed. 

Application of Brazing Metal. Care must be used to see 
that the flux and brazing wire are properly applied so that 
the metal will flow into all crevices of the joint without ex- 
cess on the surface, as no filing or abrasive wheels will be per- 
mitted either before or after the joint is brazed. 

HEAT TREATMENT OF BRAZED JOINTS 

The objects of the heat treatment of brazed joints are: 

(1) To remove internal stresses caused by brazing. 

(2) To restore ductility and toughness impaired by over- 
heating. 

(3) To enhance all the desirable physical properties as 
much as possible for each particular purpose. , Brazed joints 
to be heat treated shall not be under a strain which would 
cause the part to warp or become misplaced upon heating, as 
the furnace temperature rises too near the softening point of 
the brazing metal. Consequently any shifting of the parts 
would cau c e distortion. It is therefore necessary that all 
joints should have been previously spot welded, folded, or 
riveted in an approved manner. 

The parts shall be heated in a muffle or refractory furnace 
to a temperature sufficiently above the upper critical tem- 
perature to insure quenching at a temperature slightly above 
this point. The time the piece should be held at this tem- 
perature in the furnace depends upon the size of the piece. 
This time, however, need not be longer than required to give 
a uniform temperature to the part. Quench in oil and reheat 
to such a temperature as will give the required physical prop- 
erties. (This temperature may be obtained by trial or from 
the steel maker.) Withdraw from furnace and cool in air. 

It is to be noted that all temperatures shall be ascertained 



116 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

by the use of pyrometers, and the pyrometers shall be fre- 
quently checked to insure accuracy. 

Q. How should a good piece of steel appear that has been 
tested in a test machine? 

A. A piece of good material should show a close fibrous 
light grey texture, free from crystallization, slag, and other 
defects. 

Q. What is meant by shear test? 

A . A shear test consists of inserting a piece of metal that 
has been machined to size through a block that has a hole 
through same with center of block removed on one side, a 
detachable piece that will fit in the above mentioned slot, 
that also has a hole through same; the piece of metal to be 
tested also passes through the hole in this detachable piece, a 
load is applied on top of this detachable piece by a test 
machine until test piece has been sheared. The character 
of a good piece of material should show a clean cut or shear 
as the term applies, no torn fibers or ragged ends. 

Q. What is the torsion test? 

A. The torsion test consists of placing test piece in the 
jaws of a test machine, one head of same being held stationary 
and the other movable; turn movable head until metal 
breaks, the twisting moment is registered by a scale beam, 
and the angle through which the piece is twisted is read from 
a scale near the movable head. The nature of failure in 
ductile material would show that fibers had twisted almost 
throughout its entire length. The nature of failure ordi- 
narily, the break occurs in a plane almost at right angles to 
the axis of the bar, the end near the fixed head twists little 
and that near the movable head twists considerably; this 
test sets up shearing stresses in the bar. 



AIRCRAFT FITTINGS 117 

Q. What is a compression test? 

A. The compression test consists of placing a piece of 
material 1 inch in diameter and 2 inches in length, stood on 
end on the test machine cap and load applied. The nature 
of failure of ductile material shows cracks around its radial 
surface after cross section has about doubled by compres- 
sion; brittle materials, as hard steels, usually fail by shearing 
off diagonally, the fracture occurring at the maximum 
strength of the piece, there being little or no compression of 
the piece. 

Q. What is modulus of rupture? 

A . Modulus of rupture is sometimes defined as the inten- 
sity of stress at the instant of rupture upon a unit of section 
which is most remote from the neutral axis on the side which 
first ruptures: it is usually determined by L., inches B., and 
D., each 1 inch; it follows that the modulus of rupture is 18 
times the load required to break a bar 1 inch square, sup- 
ported at two points 1 foot apart, the load being applied in 
the middle. 

Q. What is an impact test? 

A . The impact tests consist of dropping a casting from a 
specified height, or striking same with sledge hammer blows, 
a pendulum with weight allowed to swing through a certain 
arc and striking test piece; the value of this test determines 
the soundness of the material, by the tone of sound imparted. 

Q. What is the fatigue test? 

A. The fatigue test consists of repeated applying and 
releasing load. A special design machine is used for this 
purpose. The nature of failure is similar if load is applied 
suddenly. It begins by forming crystals with each cycle, 
which eventually work their way into the interior of the 
metal, until metal finally breaks. 



118 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. What effect do the various alloying elements and 
impurities have on steel? 

A. Sulphur forms sulphides with iron and manganese; 
iron sulphide makes steel "hot short." Phosphorus forms 
iron phosphide, which is in solution with the steel and causes 
steel to be "cold short;" this causes rapid crystal growth 
while steel is heated through critical range, making refine- 
ment of grain very difficult or impossible. Silicon forms sili- 
cide with iron, which forms solid solution; it has no appre- 
ciable effect on structure of physical properties of steel. 
Manganese forms manganese sulphide, making sulphur less 
injurious, and helps to harden steels; if manganese exceeds 
90 percent, there is danger of injury in quenching mangan- 
ese steel. Nickel forms solution and lowers critical range, 
increases hardness, toughness and tensile strength with only 
a slight decrease in ductility; retards rate of change of struc- 
ture in cooling through critical range. Chromium forms 
solution imparting great hardness; retards rate of change 
of structure in cooling through critical range. Vanadium 
acts as a cleanser, removing dissolved gases; gives a very 
good combination of strength and toughness; is apt to cause 
segregation. 

Q. What does hardening of steel consist of? 

A. Hardening of steel consists of heating the steel above 
the critical range, and quickly cooling it through the critical 
range in some medium such as oil, water, or brine. 

Q. What is meant by critical range as applied to heating 
steel? 

A. The critical range means the number of degrees 
Fahrenheit used for steel when heating same without en- 
dangering the structure, namely, 1600° F., to toughen and 
temper steel, called heat treating. This consists of heating 



AIRCRAFT FITTINGS 119 

to 1600° F., quench in oil, reheat to 1100° F., and lay on the 
floor to cool; this latter is called drawing the temper; when 
a specified degree of hardness is desired, the number of de- 
grees to which metal will be heated before drawing the 
temper will vary, depending upon the degree of hardness 
required. 

Q. How is metal tested for hardness? 

A. There are two methods, both being used in testing 
the hardness of aircraft fittings, one being knownas the 
Brinell method, which consists of placing fitting or sample to 
be tested in a Brinell testing machine, then apply 3000 kilo- 
grams load, which is done by hand screw power on the small- 
er type machine. A vertical shaft contains a hardened steel 
ball at its lower extremity (the shaft being tapered at this 
end) , which makes an impression in the test piece when load 
is applied, the amount of load being shown on a glass covered 
dial on top of machine. The greater the diameter of the 
impression made in metal under test, the softer the material; 
the smaller the diameter of the impression, the harder the 
metal. The indentation is measured and referred to a table 
to determine its hardness. 

The other method is known as the scleroscope method, 
which consists of a graduated glass containing a small steel 
ball. Attached to this tube is a rubber bulb, which when 
pressed, causes the steel ball to rise in the tube to an exact 
height from which it falls on test piece placed at lower ex- 
tremity of vertical tube; the ball rebounds when it strikes 
the metal, and the higher it rebounds the harder the metal. 
The height to which it should rebound for the class of ma- 
terial being tested is known by reference to table of hardness 
corresponding to graduations on glass tube. This is the 
most rapid method known for this kind of test. 



120 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

AIRCRAFT HEXAGON HEAD BOLTS 

Aircraft bolts are made from heat-treated, cold drawn or 
cold-rolled bars, which have been heat-treated previous to 
machining. If not made from heat-treated, cold-drawn or 
cold-rolled bars, they must be heat-treated after machining 
to give metal the necessary physical properties. The above 
is not intended for engine construction. 

AIRCRAFT HEXAGON NUTS 

For todies and wings (not engines) 

Q. How many kinds of aircraft nuts are there? 

A . Six kinds, as follows : Plain hexagon, plain thin hexa- 
gon, plain slotted hexagon, plain ball hexagon, castle hexa- 
gon, castle ball hexagon. They are manufactured from cold- 
drawn or cold-rolled steel or hot-rolled steel; the material 
used shall have a tensile strength of 70,000 pounds per square 
inch, and nuts must not be hardened or tempered after 
machining. All bolts and nuts shall be zinc coated, as de- 
scribed elsewhere under rust-proofing, and after coating 
permit turning with fingers on bolt without excessive 
shake; nuts and bolts of the same dimension should be inter- 
changeable. 

AIRCRAFT WASHERS 

There are several kinds of washers used in the assembly of 
aircraft, namely: Bevel washers, both round and square, as 
well as the flat round washer. These are manufactured 
from cold-rolled or cold-drawn steel, cyanide hardened and 
zinc coated. All washers should be clean cut with both faces 
free of burrs or nicks. There is also a spring steel lock wash- 
er which prevents nut from backing off, and where used, the 
bolt end is not drilled and cottered such as is done in the case 
of the other washers where castellated nuts are used. 



CHAPTER IX 

Sand Blasting and Pickling 

Q. How are fittings cleaned? 

A. Practically all steel aircraft fittings (except threaded 
bolts or parts that may be injured, or very small parts) are 
cleaned by the sand blast process which is as follows : Sand 
blasting of large parts consists of placing same in a furnace 
like enclosure, which has a funnel shaped sand container 
about six feet above the enclosure, the sand flowing down- 
ward through a pipe by gravity, connected to this sand pipe 
at the point where it enters the enclosure is an air hose and 
by this means the sand is blown against the metal parts to 
be cleaned, thus removing the oxide, etc., the cleaned fittings 
present a light grey color. The enclosure has a door in which 
is installed a peep window of mica or celluloid, also a small 
round aperture for a man's arm, these two latter are for the 
purpose of cleaning irregular shaped fittings that would re- 
quire repeated opening and closing the large door to turn fit- 
tings, therefore, irregular fittings are cleaned by being held 
in the hand through the aperture mentioned and turned 
while being cleaned. This necessitates the operator wearing 
a long sleeve rubber glove for protection. The air pressure 
for this operation may vary anywhere from 60 to 90 pounds, 
but usually about 90 pounds. 

Q. How are small fittings sand blasted? 

A. All miscellaneous small parts (not threaded) are 
cleaned by the sand blast tumbling method. This consists 
of a perforated barrel like enclosure, which is hexagon shaped 
in cross section which revolves on a horizontal shaft in 

121 



122 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

another box like enclosure, the sand being supplied by 
gravity from an overhead container having an air hose or 
pipe connected to sand pipe, the sand being ejected into the 
revolving drum under a pressure of about 60 pounds, thus 
cleaning the fittings. 

Q. How are parts not sand blasted cleaned? 

A. Threaded metal parts and others that might be in- 
jured by the sand blast process are cleaned by the pickling 
process, which consists of what is known as the potash bath, 
using one and a-half pounds of potash to every two gallons 
of water. This solution is kept hot and an electric current is 
sometimes run through this solution while dipping of fittings 
is in progress. Fittings are usually secured to a wire, several 
in number, in order to expedite and facilitate handling. It 
only takes about 15 seconds to remove the grease and scale. 

There is also an acid and water solution that could be used, 
and is used in many instances for cleaning metal parts other 
than aircraft fittings. This latter method, however, is for- 
bidden on aircraft parts as it is injurious to the metal. 

Q. How are fittings rust proofed? 

A. After cleaning, as described above, fittings are zinc 
coated by hot dipping or zinc plating (electro galvanizing) 
provided that hot dipping shall not be used on such alloy or 
heat-treated steels as will be injuriously affected at the tem- 
peratures employed. For such steels the cold zinc plating 
process should be used. Samples should show no iron rust 
after 100 hours continuous exposure at room temperature to 
a salt spray of 20 per cent salt (sodium chloride) solution. 
The average thickness of zinc coatings on accurately dimen- 
sioned parts, screw threads, etc., should not exceed .002 inch 
in thickness, but may be of greater thickness on other parts. 



SANDBLASTING AND PICKLING 123 

It is to be noted that the copper and nickel plating of fit- 
tings have been abandoned, and zinc coating:, where coatings 
are used, is recognized as the best protection against corro- 
sion known at this time. Tin, copper, and nickel plating 
coatings, are all more or less porous and do not offer the same 
protection as zinc. 

Note: Fittings that start to corrode, after being in service, 
should be cleaned and given a coat of red lead paint, and after 
paint is thoroughly dry give same either a coat of black enamel or 
naval gray enamel paint. 



CHAPTER X 

Steel and Copper Tubes 

Steel tubes for highly stressed parts such as engine braces 
and interplane struts shall be of medium carbon steel seam- 
less tubes, cold-drawn, annealed after drawing; the tubes 
are then heat treated and quenched in oil. 

Welded steel tubes are suitable for only such parts not 
subjected to compressive stress or to high tension. These 
tubes are annealed after welding. 

A good tube whether seamless or welded should be free 
from scale, dirt, specks, longitudinal seams, laminations, 
grooves and blisters, both internally and externally. 

seamless copper tubes 

The material used is copper, 99.5 percent pure, the tubes 
being made from a cast ingot by hot piercing and rolling, and 
finished by cold drawing in such a manner as to give the 
necessary physical properties. 

All steel tubes which have closed ends have a small hole 
drilled in each end to permit the enamel to enter, and after 
tubes are drained the holes are plugged. In cases where the 
enamel is baked on the plugging of holes is done after the 
baking. The method of baking is described under the head- 
ing, "Enameling and Painting of Metal Parts" 



Note: All steel tubes are rust-proofed before enameling by zinc 
coating. 



124 



STEEL AND COPPER TUBES 125 

BRAZING MATERIAL 

The specification covering brazing spelter is as follows: 
Copper 68.0 to 72.0 per cent. 
Lead 0.3 per cent. 
Iron 0.1 per cent. 

Zinc Remainder. 

Not over 1.25 per cent impurities allowed. 
The wire in sizes from 0.187 to 0.25 inch diameter. The 
above composition applies to granulated spelter. The 
copper entering this alloy shall be 99.95 pure; the zinc of 
Virgin spelter. 



CHAPTER XI 
Enameling and Painting Metal Parts 

Q. What kind of paint is used to paint aircraft fittings? 
A. Naval gray enamel. 

Q. What is the composition of the above enamel paint? 

A. The enamel shall contain 25 to 40 per cent of pigment, 
the remainder to be high grade, water-resisting spar varnish. 

The pigment shall consist of white lead or zinc oxide or 
a mixture of the two, tinted with carbon black or lamp black 
to produce the required shade, the whole to be finely ground. 

The enamel shall not weigh more than eleven pounds per 
gallon, and the color be the standard low visibility gray. 

Q. How many methods are there for applying this paint 
to fittings? 

A. There are three methods as follows: (1) By the use 
of a brush, (2) by dipping, (3) by spraying. 

The brush or dipping methods require no description other 
than sufficient time should elapse between applications to 
allow same to become firmly set before any further applica- 
tion, all fittings receive two coats of naval gray enamel. 
The enamel shall be baked on where possible. Hollow metal 
parts, such as control horns, tubes, etc., shall be coated inside 
by filling with enamel and allowing it to drain out. Tubes 
having closed ends shall have a small hole drilled in each 
end to permit the enamel to enter, and after the surplus enamel 
has drained and the coating dried the holes shall be plugged. 
In cases where the enamel is baked on the plugging^ shall be 
done after baking. 

126 



ENAMELING AND PAINTING METAL PARTS 127 

Enameled parts which show bare spots after assembly shall 
be touched up with naval gray enamel and allowed to air dry. 

The spraying and baking process is considered the best 
and can be done more rapidly than either of the other two 
methods. The process consists of placing a large number of 
fittings on a sheet of iron supported by metal horses, the 
same being placed in a furnace like enclosure, and large fit- 
tings suspended by wires on a rack. About 6 feet overhead 
there is a paint container holding from 3 to 5 gallons of paint 
which flows downward by gravity through a hose to which a 
spra}^ gun is connected. A compressed air line hose is also 
connected to the spray gun, the end of the gun has three holes 
in same, the center hole from which the air is ejected being 
yj inch in diameter and the hole on each side for the ejection 
of the paint being somewhat smaller than the air hole. This 
arrangement of the holes produces a fan shaped spray — the 
spray gun having a trigger which starts and stops both flow 
of air and paint; the fittings having been placed as before 
stated are sprayed and turned until all parts are coated, then 
the enclosure is closed and the temperature of enclosure 
brought up to 150 to 200° F., by means of electricity, this 
being an electric furnace. There are other furnaces that can 
be used for tins purpose but the electric is considered best. 
One hour at the above temperature is usually sufficient to 
dry or bake the first coat. The above process is repeated 
with the second coat, the latter coat usually requiring a 
somewhat longer time to bake than the first or priming coat. 
Black enamel is applied the same way. 

Turnbuckle barrels, shanks, shackles, bolts, hub-fittings, 
or threaded terminals are not painted. 

Enamel paint well applied should show a uniform coating, 
no lumps, no flaking, and firmly adhering. A good test for 
enamel consists of bending material without breaking the 
enamel; there are other tests prescribed to determine resist- 



128 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

ance to water, gasoline, hardness, etc., which are of value 
only to inspectors in conducting; tests. 

BLACK ENAMEL 

Q. For what purpose is black enamel used and what is its 
composition? 

A. Black enamel is intended for general use on aircraft 
fittings, such as handrails, small metal parts, etc. It may 
be used either as an air drying or baking enamel. It is com- 
posed of spar varnish with 5 per cent of carbon black added. 

Q. What is wire and cable enamel and for what purpose 
is it used? 

A. It is an enamel composed of spar varnish with 5 per 
cent of pure American blue (ferri-ferro cyanide). This 
enamel is intended for use on fixed external wires or cables, 
fixed internal hull wires or cables, and all internal wing wires 
or cables. 

When dry, it presents a semi-transparent blue film, can 
be applied by brush or dipped and allowed to drain. 



CHAPTER Xll 

Fabrics and Their Application 

Q. How many kinds of fabric are used in seaplane con- 
struction, and where used? 

A. There are three kinds of fabric used in seaplane con- 
struction, namely, linen, (Grade "A"), linen, (Grade "B"), 
mercerized cotton, (Grade "A"), and cotton sheeting. Grade 
"A" linen is used for the covering of wings, rudders, elevators, 
stabilizers and ailerons. Grade "B" linen is used for fuselage 
covering, top, bottom, and sides. Grade "A" mercerized 
cotton is used for all purposes for which both Grade "A" and 
Grade "B" linen are used. Cotton pontoon sheeting is a 
fabric used between the inner and outer layers of the bottom 
planking of flying boats, on pontoons between the inner and 
outer layers of deck planking, as well as the inner and outer 
layers of bottom planking. 

Q. What are the characteristics of the fabrics mentioned? 

A. The linen, both grades "A" and "B", are made of the 
finest unbleached flax fiber, and are distinguished from each 
other by thread count and tensile strength. Grade "A" 
linen must have at least 90 threads to the inch in warp, and 
not more than 105 threads to the inch in the filling. Grade 
"B" linen must have at least 60 threads to the inch in warp, 
and not more than 90 threads to the inch in filling. The 
fabric under normal moisture conditions must not weigh 
more than 4.5 ounces per square yard, width not less than 
36 inches. The linen is tested for tensile strength by cutting 
samples from various bolts of cloth, 8 inches in length and 
li inches in width, then pull off threads on both sides of 

129 



130 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

sample until it measures 1 inch in width; place sample be- 
tween upper and lower jaws in a test machine with 6 inches 
between the jaws, allowing 1 inch for gripping by the jaws 
at each end. The samples are cut in both directions from 
the bolt, in order that both warp and filling strength can be 
determined, the pulling jaw to move at a rate of 12 inches per 
minute during test. The minimum strength shown by grade 
"A" linen samples for both warp and filling shall be 75 
pounds. Grade "B" linen shall show a minimum breaking 
strength, for both warp and filling, of 65 pounds. 

Grade "A" mercerized cotton is manufactured from staple 
cotton not less than 1 J inches in length. There shall not be 
less than 80 threads and not more than 84 threads per inch 
in both warp and filling. To be of plain weave, and not 
weigh more than 4.5 ounces per square yard under normal 
moisture conditions; width 36 inches. Samples are cut from 
bolts to be tested from both directions. The test samples 
for cotton are longer than those for linen, being 12 inches in 
length with 8 inches space between pulling jaws, which travel 
at a speed of 12 inches per minute during test, and shall show 
a breaking strength of 80 pounds for both warp and filling.. 
It is to be noted that this cotton fabric is stronger than linen 
fabric of either grade. The cotton sheeting referred to, that 
is used on flying boats between bottom planking, is of no 
special manufacture, except it is of high grade. Nainsook 
of high commercial grade is also used between deck and bot- 
tom layers of planking of pontoons. The following is the 
latest practice in vogue for covering the various parts of an 
aircraft with fabric : 

Thread used for fastening the fabric to ribs and other 
parts of the machine shall be heavy linen thread and waxed 
before using. 

Thread used for machine stitching of seams shall be silk 
thread, grade "B." 



FABRICS AND THEIR APPLICATION 131 

Thread used for hand stitching of seams shall be light linen 
thread, and shall be waxed before being used. 

Tape used over lacing, or for the protection of edges, cov- 
ering of tacking, or similar purposes shall be made from linen 
or cotton. The tape shall be of sufficient width for the pur- 
pose for which it is to be used. The edges of the tape shall 
be frayed by extending the filling threads } to \ inch beyond 
the body of the tape on each side. 

The special reinforcing tape used under lacing loops shall 
be linen or cotton tape \ inch wide of an approved quality 
and strength. 

Dope used for cementing of tape to fabric shall be the same 
dope as is used for the shrinking of the fabric. 

Fabric used for pontoon, hull, or float covering shall be 
cotton pontoon sheeting of an approved quality. 

The fabric covering shall be applied to the wings and 
auxiliary surfaces, so far as is practicable, by the envelope 
method. An envelope shall be made by sewing the fabric 
together. This envelope shall be drawn over the surface to 
be covered, drawn taut, and the open part securely stitched. 
After completion of the operation the tension in the fabric 
must be approximately the same in all directions. 

All seams shall be folded-ply seams and shall be double 
sewed, preferably by means of a double-needle sewing ma- 
chine, equipped with a folder attachment. Ten stitches per 
inch shall be used. The row of stitches nearest the edge of 
each side of seam shall be about xV inch distant from it and 
the two rows of stitches shall not be more than f inch nor 
less than \ inch apart. Seams must not follow ribs so that 
the lacing would be through or over the seam. 

Envelope closing seams shall be made at the trailing edge 
in preference to the leading edge where practicable. 

The fabric shall be applied on the wings with the woof or 
filling threads running at an angle approximately 90 degrees 
to the ribs. 



132 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

The fabric may be applied to the body or auxiliary surfaces 
with woof or filling threads running at an angle to the center 
line or ribs, respectively, of approximately 45 degrees or 90 
degrees as the contractor may decide. In any case the fabric 
should be similarly applied to each machine or corresponding 
part of machine on any order. 

Fabric shall be attached to wings and auxiliary surfaces 
by the tape and lacing method. 

Lacing of the fabric to ribs shall extend along the rib to 
within a distance from the leading and trailing edges equal 
to the distance between lacing points. Lacing shall be at 
2-inch intervals on all surfaces. 

Under the lacing loops, on each side of all surfaces with 
the exception noted, a special linen or cotton tape shall be 
used. On the upper side of wing surfaces a rattan strip may 
be used in place of reinforcing tape. 

The lacing shall be done by passing the thread through the 
aerofoil from one surface to the other, including in each loop 
the rib as well as fabric and reinforcing tape or rattan on each 
side. The first loop shall be fastened with a slip knot, se- 
cured. Each succeeding loop, including the final, shall con- 
sist of a half hitch knotted around the part of the thread 
leading from the preceding loop. 

The lacing shall be made with one continuous piece of 
thread for each rib, the thread carried from loop to loop being 
located on the upper side in the case of horizontal surfaces. 
In the case of vertical surfaces, the thread from loop to loop 
shall be located on alternate side over adjacent ribs. Lacing 
must be taut at all points when completed and before applica- 
tion of dope. 

After completion of lacing, application and drying of the 
first cost of dope, frayed-edge finishing tape, shall be cement- 
ed to the fabric, over the lacing on each side, using dope to 
fasten it in place. 



FABRICS AND THEIR APPLICATION 133 

On all edges of all wing panels and control surfaces the 
fabric shall be reinforced by a strip of frayed-edge tape run- 
ning the full length of and folded back over the edge. This 
tape shall be cemented in place with dope. 

Where the fabric is pierced by bolts, etc., it shall be rein- 
forced by means of a patch having edges frayed f to J inch. 
This patch shall be applied after the first coat of dope has 
dried and shall be cemented in place by the use of dope. 

Where the fabric is permanently tacked to wood parts it 
shall be doubled back on itself before tacking, and the tacks 
used shall be brass, tinned iron, monel metal, or copper 3 oz. 
tacks. 

Where the fabric comes in contact with metal parts, these 
parts shall be coated with naval gray enamel, and, when 
possible, shall be baked. 

All fabric-covered wings and auxiliary surfaces shall be 
provided with efficient means for drainage of condensation, 
etc. The use of rust-proof metal eyelets or grommets 
through the fabric, located at the normally lowest points in 
each surface, is satisfactory for this purpose. 

Where fabric is used for covering of hulls, pontoons, floats, 
etc., it shall be drawn taut and cemented in place by means 
of an approved marine glue. The fabric may be ironed after 
application to improve the penetration and adhesion of the 
glue. 

After the glue has thoroughly set, the surface of the fabric 
shall be finished as required. If the surface is sand-papered 
in the process of finishing, this must be done very lightly and 
the fabric must not be injured thereby. 

Fabric used in the construction of laminated bulkheads 
shall be cemented in place with an approved marine glue. 

Solid or laminated struts shall not be fabric covered. 
Laminated struts, however, shall be taped at their mid sec- 
tion with a 4-inch band of fabric, and cemented in place with 
casein or hide glue, preferably the former. 



134 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

COTTON HULL SHEETING 

Use 

1. This specification covers the general manufacture of 
hull sheeting that is applied with marine glue to the outer 
surfaces of hulls of naval aircraft, 

Material 

2. The sheeting shall be made from cotton of not less than 
1-inch staple. 

Manufacture 

3. The warp and filling yarns shall be alike. The yarn 
shall be single ply. There shall be not less than 68 threads 
per inch in the warp and 72 threads per inch in the filling. 
The weave shall be plain. 

Weight 

4. The weight shall not be less than 5.2 ounces per square 
yard as determined according to the method given below. 

Finish 

5. The material shall be subjected only to the usual gray 
room processes. 

Tensile Strength 

6. The tensile strength of the finished material shall not be 
less than 55 pounds in the warp or filling as determined ac- 
cording to the method given below. 

Methods of Tests 

7. The weight specimens shall be exposed to an atmosphere 
of 65 per cent relative humidity at 70° F., for a period of three 
hours and the weight determined in this atmosphere. 



FABRICS AND THEIR APPLICATION 135 

The tensile strength shall be determined from five strips 
6 inches long by 1| inches wide, cut from both the warp and 
filling directions of the fabric. These strips shall be raveled 
to 1 inch in width and allowed to remain in an atmosphere 
of 65 per cent relative humidity at 70° F., for a period of three 
hours and then tested in this atmosphere. At the end of 
that time the specimens shall be placed in the clamps of the 
testing machine with 3 inches between clamps and caused to 
rupture by moving the pulling clamp at the rate of 12 inches 
per minute. 

COTTON PONTOON SHEETING 

Use 

1. This specification covers the requirements for cotton 
sheeting to be used between the inner and outer skins of pon- 
toons and similar construction on naval aircraft. 

Material 

2. The sheeting shall be made from cotton of not less than 
1-inch staple. 

Manufacture 

3. The warp and fining j^arns shall be alike. There shall 
be not less than 100 threads nor more than 108 threads per 
inch in either warp or filling. The weave shall be plain. 

Weight 

4. The weight shall be not more than 3.75 ounces per 
square yard as determined according to the method given 
below. 

Finish 

5. The material shall be subjected only to the usual gray 
room processes. 



136 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Tensile Strength 

6. The tensile strength of the finished material shall be not 
less than 45 pounds per inch in either the warp or filling as 
determined according to the method given below. 

Methods oj Test 

7. The weight specimens shall be exposed to an atmosphere 
of 65 per cent relative humidity at 70° F., for a period of three 
hours and the weight determined in this atmosphere. The 
tensile strength shall be determined from five strips 6 inches 
long by li inches wide, cut from both the warp and filling 
directions of the fabric. These strips shall be raveled to 1 
inch in width and allowed to remain in an atmosphere of 65 
per cent relative humidity at 70° F., for a period of three 
hours and then tested in this atmosphere. At the end of 
that time the specimens shall be placed in the clamps of the 
testing machine with 3 inches between clamps and caused to 
rupture by moving the pulling clamp at the rate of 12 inches 
per minute. 

FIREPROOFING OF AIRPLANE FABRIC 

Previous to the application of Acetate Dope as described 
elsewhere in this book, the fireproofing of fabric on fuselages 
and wings consists of the fabric being coated with a 15 per 
cent solution of commercial ammonium phosphate. The 
solution is prepared by dissolving 1| pounds of commercial 
ammonium phosphate in a gallon of cold or lukewarn water. 
The solution will always have the odor of diluted ammonia 
water so it should be kept (preferably) in closed vessels, 
otherwise the evolution of the ammonia will change the 
nature of the compound. The best procedure is to prepare 
just enough solution to treat the desired quantity of fabric. 



FABRICS AND THEIR APPLICATION 137 

The fabric may be treated after it is on the airplane by 
brushing the ammonium phosphate solution into the fabric 
or before placing it on the airplane by immersing the fabric 
in the solution. If the first method is used the fabric should 
be thoroughly saturated with the solution and then suffic- 
ient time should be allowed for the fabric to dry thoroughly 
before the application of the dope. If the second method of 
treatment is used the fabric after immersion should be sus- 
pended under tension so that it will dry free of wrinkles. 

The fireproofing of airplane fabric as above described is 
now the standard practice on all airplanes now under con- 
struction. 

The following navy standard doping system shall be used 
on all fabric-covered surfaces of all airplanes (excepting only 
such cases where the fabric is glued in place, as is the case 
with fabric-covered hulls). On all fabric two coats of cellu- 
lose acetate dope shall be applied. This shall be followed 
by the application of a sufficient number of coats of cellulose 
nitrate dope to obtain satisfactory tautness and finish but 
in no case shall less than two nor more than four coats of 
nitrate dope be applied. Sufficient drying time shall be 
allowed between each of the coats of dope (about 30 minutes.) 

After the last coat of dope has dried for not less than 12 
hours aluminum paint shall be applied, two coats being used 
on all vertical surfaces, two coats on upper side and one coat 
on the lower side of all horizontal surfaces. 

Q. How would you repair large or small tears in wing 
fabric? 

A. In making repairs to a large rip or tear, sew tear to- 
gether using No. 30 linen thread and the baseball stitch. 
After that is done apply acetone, which is a solvent to re- 
move paint, dope, etc. If place to be repaired is close to a 
rib, cut out the patch to be applied sufficiently large enough 



138 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

to extend beyond the rib about 3 inches. Apply a coat of 
dope over the surface that has been cleaned, and stitch patch 
in place, having frayed its edges, then dope over same and 
paint as rest of wing. If tear was adjacent and parallel to 
the rib, a few lacings should be made around the rib and 
about 4 inches apart in between previous lacings. Tape 
over lacing for a small tear same as above. When a tear 
occurs near a fitting it is best to remove the fitting in order 
that a proper repair can be made. 

Q. What precautions are necessary when covering a new 
wing or re-covering an old wing? 

A. It is important to have wings or any fabric covered 
part straight and in line before covering and doping, other- 
wise it is extremely difficult to straighten same if twisted or 
out of line after covering and doping. If care is taken to 
give the fabric a uniform tension before doping, and dope is 
applied uniformly, there is very little danger of twisting the 
panel, but if such does happen it may be corrected by two 
methods, as follows: By applying more dope to increase the 
tension at some slack point which may correct the twist, or 
if the twist is induced by too much tension in some part of 
the panel, use acetone to slacken same and weight panel 
until it comes to its proper shape and will remain so. After 
doping, in all cases stand panel on its leading edge. 



CHAPTER XIII 

Material Used in the Construction of H-16's and 
Other Flfing Boats 

Keel. Ash — possible substitute white oak, rock elm. 

Keelson. Basswood — possible substitute white pine. 

Floors. Basswood — possible substitute white pine. 

Stempost. Ash — possible substitute white oak, rock elm. 

Breast hooks. Ash — now made of metal. 

Longerons. Ash. 

Sidewalk beams. Spruce — possible substitute Douglas fir. 

Stringers, forward, 7 foot. Ash— possible substitute white 
oak, rock elm. 

Stringers, after, 18 foot. Spruce — possible substitute 
Douglas fir. 

Note: The ash and spruce stringers are spliced together. 

Nose frames. Ash — possible substitute white oak. 

Seam battens. Ash — possible substitute white oak. 

Side planking. 3 ply Haskell veneer. 

Shelf stringers. Ash. 

Bulkheads. 3 ply Haskell veneer. 

Washboards. Spanish cedar. 

Nose planking. Spanish cedar. 

Fin top framing. Ash — possible substitute white oak. 

Gunners cockpit combing. Ash — possible substitute rock 
elm. 

Gunners cockpit backing. Ash — possible substitute rock 
elm. 

Fin stringers. Ash — possible substitute, white oak — rock 
elm. 

139 



140 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Bulkhead stiff eners. Spruce — possible substitute Douglas 
fir. 

Diagonal pillar braces. Spruce — possible substitute Doug- 
las fir. 

Beam struts, center. Spruce — possible substitute Douglas 
fir. 

Fin planking top. Haskell veneer. 

Bottom and step planking. Spanish cedar. 

Tank stringers. Spruce — possible substitute fir. 

Tank rings. Ash — possible substitute white oak, rock 
elm. 

Tank floors. Spruce — possible substitute fir. 

Floor bearers. Spruce — possible substitute fir. 

Floor slats. Spruce — possible substitute fir. 

Seat back brace. Spruce — possible substitute fir. 

Foot rest. Spruce — possible substitute fir. 

MOULDINGS 

Fin edge. Ash. 

Fin top corner. Mahogany. 

False keel on bottom. Ash. 

PARTS TO BE BENT 

Bow keel, longerons, outer fin members or chine, bow 
combing, nose ribs, floor stringers, tank rings, deadwood 
wood for sternpost, seam battens, breast hooks if made of 
wood. 

The above woods are practically the same used in the con- 
struction of the F-5-L type of flying boat, and it is to be 
remembered that in replacing or repairing any broken or 
damaged part to use a similar material in doing same, or one 
of the substitutes permitted. Do not use spruce or pine to 
replace a section of ash or oak, and where replacing a bent 
or curved piece of ash, oak or rock elm, the piece of material 



MATERIAL USED IN FLYING BOATS 141 

must be steamed and bent to shape before being used, other- 
wise you set up what is known as an initial stress, which 
has a tendency to tear away from its fastenings or throw 
something out of line. 

In the construction of the bottoms of all types of pontoons, 
or flying boats, are what are knows as steps. In pontoons for 
seaplanes there is one step, it being a break in the form of the 
bottom about two-thirds the length of pontoon from the 
nose, and aids in breaking the suction when getting off the 
water. The larger type of flying boats have two steps on 
each side of keel, shaped like an elongated V, and consists 
of securing several stringers to the boat's bottom, the thin 
or tapered ends pointed forward, and on the rear end meas- 
uring 2J inches. This is planked over, the forward ends 
being flashed with sheet copper, thus offering no resistance 
to the forward motion to the boat. It can be seen that this 
forms a long V shaped pocket on the bottom of the boat, 
and there are two of these on each side of the V bottom. In 
addition to the foregoing, there is provided what is known 
as breather tubes to break the vacuum, thus permitting the 
seaplane or flying boat to leave the water readily. In the 
pontoons they are installed a few inches abaft the step, and 
are placed vertically, running from the top to the bottom of 
the pontoon, one on each side of the keel about 6 inches there- 
from. These breather tubes are made of light sheet copper, 
the ends being flanged and secured to the top and bottom 
planking, tubes being approximately 2 inches in diameter. 
The H-16 has no breather tubes, but two steps only. The 
H-S-2-L has one step of a similar design as a pontoon, and 
has two breather tubes. These are placed on the inside of 
the hull in a vertical position and get air through the cock- 
pit openings. The original design for the F-5-L type of 
boats did not call for breather tubes, but some were later 
installed similar to those in the H-S-l-L type; also breather 



142 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

tubes have been placed on the fins, close in to the side plank- 
ing between the top and bottom fin planking. 

It is to be noted that, in the construction of the rear part 
of an H-16 or F-5-L type of flying boat where the fuselage 
type of construction comes into play, the struts between 
the upper and lower longerons on each side are of metal 
tubing, also the transverse braces between the upper long- 
erons are metal. This is done in order to get greater strength, 
and in order to facilitate fastening to these struts and braces 
they are covered with two pieces of spruce wrapped with 
tape and dope, thus maldng same rectangular in section. 
Metal tubes of similar design but not wood covered are used 
in the place of compression ribs in the construction of the 
large and heavier type of wing panels. 



CHAPTER XIV 

Glues Used in Aircraft Construction 

Q. How many kinds of glue are there used in aircraft 
construction? 

A. Three kinds as follows: Certified hide glue, certified 
casein glue, marine glue. 

Q. Where are the above named glues used? 

A. Certified hide glue is used for all high class work 
where non-water resisting glue is permitted, such as pro- 
pellers, laminated struts, wing spars, splices, etc., or where 
parts do not come in contact with water; this glue is also 
used in glueing veneer and plywood together. The method 
for mixing and applying this glue and the necessary precau- 
tions to be taken with same are described in detail under the 
description of the manufacture of a propeller. 

Casein glue is used for all purposes that certified glue is 
used for except propellers. It did not come into use until the 
latter part of 1918, the basis of this glue being powdered 
dry milk, the other components being a trade secret. The 
formula is said to have been discovered by two brothers who 
resided in Switzerland, and the formula purchased by an 
American concern. Tests have proven that if this glue is 
handled as per manufacturer's directions it is the strongest 
glue known in the world today. The writer has witnessed 
tests conducted with this glue wherein three blocks of wood 
were glued together and a load applied in a test machine on 
the center block, ana the outer blocks would give way with- 
out disturbing the glue. However, this glue must never be 
used unless the person using same is familiar with the method 

143 



144 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

of mixing and applying same. In general this glue is mixed 
with water, and must be applied within 30 minutes after 
mixing, otherwise it will lose its physical properties. 

Marine glue is used for securing the fabric to the hulls of 
H-S-l-L flying boats, also in connection with the fabric 
placed between the inner and outer layers of bottom plank- 
ing, the process of application being to apply a coat of glue 
to the under side of the first layer of planking, lay on the 
fabric smoothly, then give fabric a coat of glue before placing 
the outer layer of planking in place. The properties of this 
glue are that it is water resistant, being in contrast to the 
other mentioned glues which set hard and firm, whereas 
marine glue does not, but remains elastic. 

Note: No other glues should be used on aircraft, unless it is 
authorized by the Bureau of Aeronautics. 



CHAPTER XV 
Dopes and Solvents 

Q. How many kinds of dopes and solvents are there, and 
for what purpose are they used? 

A. Three kinds of dope and two kinds of solvents are 
used on aircraft: Acetate dope on fabrics used on airplanes 
to tauten and secure greater fire proofing qualities; Nitrate 
dope is used to tauten, strengthen and make the fabric imper- 
vious to moisture; Airship dope is used on lighter-than-air 
craft, such as airships, kite and free balloons — it closes the 
pores in the fabric and lessens diffusion. Airship dope thin- 
ner and solvent is the same material, being used to thin 
airship dope when it gets too thick to apply readily either 
by hand or spray gun. It is also used for removing dope 
from airship fabric when patches or similar repairs are to 
be made. Dope solvent is used for removing enamel and 
dope from wing and tail surfaces of airplanes when repairs 
are to be made to the fabric. 

Note: In many cases it is very difficult to tell the difference be- 
tween the cellulose acetate dope and cellulose nitrate dope. The 
following is a method whereby the two dopes may be distinguished. 

Pour a small quantity of the dope upon a glass or smooth 
metal plate. The dope will gradually solidify with the form- 
ation of a film. Allow this film to dry for at least 24 hours 
and then remove it from plate, set fire to the film and note 
the rate of burning. If the film has been made from nitrate 
dope it will burn with great rapidity and with a flashy flame. 
If made from acetate dope the film will burn with a slow 
steady flame. It is suggested that if the two dopes are 

145 



146 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

available that this test be conducted as this will give an idea 
of their comparative rates of burning and will make it less 
difficult to distinguish an unknown dope. 

Care should be taken to see that dope is in good condition 
before being applied to the cloth as the constituents of the 
dope deteriorate with age. If the dope has become darkened 
it should be tested for acidity before being used. If facilities 
are not available a half gallon sample should be forwarded 
to the Bureau for test. In all events the dope should be 
tested on a small piece of cloth before being applied to the 
cloth covered parts. 



CHAPTER XVI 
Aircraft Paints and Insignia 

Q. How marry kinds of paint, dope or varnish are used 
on an aircraft, and where used? 

A . There are six kinds of paint used on aircraft, namely : 
Naval gray enamel for hulls and pontoons and struts if 
painted, also fittings. Aluminum wing enamel for wings; 
black paint for numbers, also black enamel on fittings; red, 
white and blue for insignia. 

There are two kinds of varnish used: Spar varnish for 
wing panels before being covered, interior of flying boat hulls 
(except in cockpits where shellac varnish is used, which is 
not solvent in gasoline), on interplane struts if not painted 
like N-9s, and generally throughout the machine. 

Shellac varnish is used in cockpits, and as a filler for a first 
coat for propellers. 

AIRCRAFT INSIGNIA AND MARKING 

Use 

1. The distinguishing insignia and marking herein de- 
scribed are for use on all United States Naval aircraft. 

Insignia Design 

2. The insignia design shall be a red circle inside of a white 
five-pointed star inside of a blue circumscribed circle. The 
construction is obtained by marking off five equi-distant 
points on the circumference of the circumscribed circle and 
connecting each point to the two opposite points. The outer 
parts of the fines thus obtained from the points of the star, 

147 



148 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

and the red inner circle is made tangent to the sides of the 
pentagon formed by this construction. 

3. Dimensions. The diameter of the circumscribed circle 
shall be 5 feet, except that where the chord length of the 
wing is less than 5 feet, in which case the diameter shall be 
equal to the chord length. 

4. Direction. On vertical surfaces one of the points of 
the star shall point directly upward and on horizontal surfaces 
one of the points of the star shall point directly forward. 

5. Color. The shades of red, white, and blue shall be the 
same as those used in the United States flag. 

Marking 

6. Building Letters and Numbers. The building letters and 
numbers to be painted in black on the aircraft as hereinafter 
described are arbitrary symbols, assigned by the Department 
for the purpose of referring to a component unit such as 
the car or the envelope of an airship. 

7. Class Letters and Numbers. The class letters and num- 
bers to be painted in blue on the aircraft as hereinafter de- 
scribed are arbitrary symbols assigned b> the Department 
to designate the aircraft and should not be confused with 
the building letters and numbers referred to in paragraph 6. 

8. Example. Airship car number A-4118 and envelope 
E-103, when assembled with a set of control surfaces, form 
airship D-l, i.e., the first airship in the D class. Should 
manufacturing necessity intervene, any or all of the com- 
ponent parts may be changed, but the completely assembled 
airship would still be desigated as D-l. A subsequent 
type would be "E" or "F" class airship. 

9. Piece Numbering. All individual metallic fittings, except 
standard parts, such as bolts, nuts, washers, turnbuckles, 
swaged and stream-line wire terminals and shackles, shall 



PAINTS AND INSIGNIA 149 

be marked with the manufacturer's piece number. The 
number shall be in raised letters when possible and as large 
as practical. 

10. Manufacturers' Identification Plate. On each aircraft 
of any type, there shall be placed on each instrument board 
a metal plate, transfer, or other convenient means (the size 
of which shall not exceed 3 inches by 6 inches) the following 
information : 

(1) Name, trade-mark, and address of aircraft manu- 
facturer. 

(2) Manufacturers' model and serial number. 

(3) Navy model, class, and serial number. 

(4) Date of delivery (approximate) . 

11. The name or trade-mark of the manufacturer shall 
appear on the aircraft in no conspicuous location other than 
that specified above, and in any case such other location must 
be specifically approved in writing by the Bureau. 

AIRPLANE INSIGNIA AND MARKING 

12. Insignia. Four insignia will be placed on the wings of 
each airplane. One shall be placed on the upper surface of 
each upper wing, in such a position that the circumference of 
the circumscribed circle just misses contact with the aileron 
and one shall be placed on the corresponding position, on the 
lower surface of each lower wing. 

13. Both sides of that portion of the rudder which is in 
rear of the rudder post shall be painted with three equally 
wide bands, parallel to the vertical axis of the airplane and 
colored red, white, and blue, of the shades specified in para- 
graph 5. The blue band shall be nearest the rudder post, 
the white band in the center, and the red band at the tail of 
the rudder. 

14. Marking. The building letter and number, assigned 
by the Department and specified in the contract, shall be 



150 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

painted in 3-inch black figures on each side of the rudder, at 
the top of the white band. Also the building letter and num- 
ber shall be placed, in 12-inch black figures, on the sides of the 
body, midway between wings and rudders. 

15. All struts shall be numbered at the bottom, in 1-inch 
black figures, and corresponding black numbers shall be 
painted on the top of lower wing panels close to the strut 
fittings. The front outermost strut, on the right of the pilot, 
shall be numbered (1), and all the remaining front struts 
shall be marked in order, from right to left, with consecutive 
odd numbers. The rear outermost strut, on the right of the 
pilot, shall be numbered (2) and all the remaining rear struts, 
from right to left, shall be marked with consecutive even 
numbers. 

16. A code of letters and figures shall be used to designate 
the doping system and date of application. These designa- 
tions shall be black letters 1 inch high and placed on the 
underside of the fuselage, wings, and control panels. The 
code provides for a letter or letters to be assigned to each fin- 
ishing material, with the figures following to indicate the 
number of coats and date of completion. The finishing ma- 
terials, in accordance with Bureau of Construction and Repair 
aeronautical specifications, have been given the following 
designating letters: 

Acetate dope A D 

Nitrate dope N D 

Naval gray enamel E 

Spar varnish V 

Wood filler W 

Shellac S 

Aluminum wing enamel A 

17. For example, the code AD2, ND3, E2, 10-8-18 would 
mean: Acetate dope, two coats; nitrate dope, three coats; 



PAINTS AND INSIGNIA 151 

naval gray enamel, two coats; the work being finished Oc- 
tober 8, 1918. 

AIRSHIP INSIGNIA AND MARKING 

18. Insignia. Two insignia, 5 feet in diameter, will be 
placed on the envelope of each airship, one on top and one on 
the bottom, the center of each insignia being on a line estab- 
lished by the intersection of a vertical longitudinal axial 
plane with the envelope. The center of the top insignia shall 
be on this established line, and at the greatest diameter of the 
envelope. The center of the bottom insignia shall be on the 
established line, 3 feet back of a point midway between the 
front of the car and the tip of the bow of the envelope, meas- 
ured horizontally. 

19. The rudders and elevators of each airship will be 
marked in a manner similar to that required for airplane rud- 
ders in paragraphs Nos. 13 and 14. The bands shall not 
exceed 5 feet in length, or 18 inches in width, and where there 
is more than one rudder only the outboard side of each out- 
board rudder will be marked. 

20. Marking. The class letter and number designating 
each airship, assigned by the Department and specified by 
the contract, together with the words, "U. S. Navy," where 
hereinafter specified, shall be painted on fabric and affixed 
to the envelope. Light empennage fabric, preferably of the 
same color as the envelope, shall be used. 

21. Three sets of class letters and numbers shall be affixed 
to the envelope, one set on each side, preceded by the words 
U U. S. Navy," the center of the letters and wording being 
over the center of the car, and one under the bow, the centre 
being 10 feet 6 inches forward of the center of the lower 
insignia. 

22. The letters and figures shall be 54 inches high and the 



152 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

color used shall be blue, of the shade of blue used in the 
United States Flag. 

23. The building letters and numbers, designating each 
set of control surfaces and corresponding stabilizers or fins, 
shall be painted in 3-inch black letters, on each side. 

24. The letters and numbers, on the upper surfaces, on 
either right or left side, shall be so placed that the bottom of 
the letters and numbers is outboard in each case. 

25. The letters and nunibers, on. the under surfaces, on 
either right or left side, shall be so placed that the bottom 
of the letters and numbers is inboard in each case. 

26. The letters and numbers, on the vertical surfaces, 
shall read from forward aft on the left side and from aft for- 
ward on the right side. 

27. The letters and numbers, on the elevators, shall be 
painted on the white band, in such location that the top of 
the letters or numbers is 3 inches from the inboard margin 
of the band. 

28. The letters and numbers, on the rudders shall be 
painted on the white band, in such location that the top of 
letters or numbers is 3 inches, from the top margin of the 
band. 

29. The letters and numbers, on the fins or stabilizers, shall 
be painted on their surfaces in direct line with the letters and 
numbers, on the control surfaces and 6 inches forward of the 
rear edge, of the fin or stabilizer. 

30. The building letter and number of the car, assigned by 
the Department and specified in the contract, shall be painted 
in 3-inch black figures on each side of the car, at about the 
midpoint of its length and level with the top longitudinal 
member. 

31. The building letter and number of the envelope, as- 
signed by the Department and specified in the contract, shall 
be painted in 3-inch black figures, only on the lower side and 



PAINTS AND INSIGNIA 153 

just aft of the lower insignia. The top of letters and num- 
bers shall be the nearer to the insignia. In case the color of 
the envelope is such that black figures are not readily dis- 
tinguishable, there shall be painted a white background, 
with 1-inch margin, about these building letters and numbers. 

FREE BALLOONS, INSIGNIA AND MARKING 

32. Insignia. For United States Navy spherical balloons 
two insignia, 5 feet in diameter, shall be placed on the enve- 
lope, one at each end of a diameter which is inclined 45° to 
the vertical axis of the balloon. 

33. Marking. The words "U. S. Navy" shall be painted 
on fabric and affixed to the envelope centered on each end of 
a horizontal diameter, in a vertical plane, perpendicular to 
the plane passing through the centers of the insignia. 

34. Light empennage fabric, preferably of the same color 
as the envelope shall be used. The letters shall be 54 inches 
high and painted with the shade of blue same as blue used 
in the United States Flag. 

35. The building letters and numbers, assigned by the 
Department and specified in the contract, shall be painted 
on the envelope 3 inches below the lower insignia, the letters 
and figures to be black, 3 inches high. In case the color of 
the envelope is such that black figures are not readily dis- 
tinguishable, there shall be painted a white background, with 
1-inch margin, about these building letters and numbers. 

KITE BALLOONS, INSIGNIA AND MARKING 

36. Insignia. Two insignia, 5 feet in diameter, shall be 
placed on each kite balloon, one on top and one on bottom of 
the envelope, the center of each insignia to be at the inter- 
section of a vertical plane, through the longitudinal axis, 



154 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

with a vertical plane through the greatest diameter of the 
envelope. 

37. Marking. The words "U. S. Navy" shall be painted 
on fabric and affixed to each side of the envelope, on the lon- 
gitudinal center line, approximately midway between the 
nose and the forward end of the empennage. 

38. Light empennage fabric, preferably of the same color 
as the envelope, shall be used. The letters shall be 54 inches 
high and painted with the shade of blue same as blue used in 
the United States Flag. 

39. The building letters and numbers, assigned by the 
Department and specified in contract, shall be painted on the 
envelope 3 inches aft of the lower insignia, the letters and 
figures to be black, 3 inches high. In case the color of the 
envelope is such that black figures are not readily distinguish- 
able, there shall be painted a white blackground, with 1-inch 
margin, about these building letters and numbers. 

MARKING OF PIPES 

In addition to the foregoing, the various pipes of an air- 
craft are painted as follows: All piping shall be marked with 
colored bands, about one-half inch wide, painted on pipe, 
near each end and at intermediate points not over 24 inches 
apart, in accordance with the following system: 

(a) Fuel pipes: Red. 

(b) Oil pipes: White. 

(c) Air (except starter) pipes: Blue. 

(d) Water pipes: Yellow. 

(e) Starter pipes: Black. 



CHAPTER XVII 

Aluminum and Its Alloys 

Q. For what purpose is sheet aluminum used? 

A. Sheet aluminum is used for cowling around engines 
on the forward part of the fuselage, for streamlining in some 
instances, back rests for scarf ring gun mounts. 

Q. What are the characteristics of sheet aluminum? 

A. Sheet aluminum should show by chemical analysis a 
minimum of 98 per cent aluminum. Test specimens cut in 
any direction from a sheet should show results as shown in the 
following table: 



CONDITION 


THICKNESS 


TENSILE 

strength 
(mini- 
mum) 


elongation' 

(minimum) 
in 2 inches 




Gage 
number 
(B. & S.) 


Inches 


Pounds 

per square 

inch 


50.8 mn. 

PER CENT 


Hard -rolled 

Half -hard j 

Soft-annealed. . . 1 


10 to 26 

10 to 16 

18 to 26 

10 to 16 
18 to 22 
24 to 26 


0.102 to 0.016 

0.102 to 0.051 
0.040 to 0.016 

0.102 to 0.051 
0.040 to 0.025 
0.020 to 0.016 


22,000 

18,000 
18,000 

12,000 
12,000 
12,000 


2 

7 
5 

30 
20 
10 



Good sheet aluminum in addition to the above should be 
sound, flat, free from buckles, seams, discolorations or other 
defects. A test piece of soft-annealed sheet aluminum should 
bend back against itself without cracking. Half hard sheets 

155 



156 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

should bend through an angle of 180° on a radius equal to 
the thickness of the sheet without cracking. 

Tolerances on thicknesses of sheets are permitted as 
follows : 



THICKNESS, AMERICAN WIRE 
GAGE (B. & S.) 


TOLERANCES 




inch 


10-11 


0.003 


12-14 


0.003 


15-17 


0.003 


18-20 


0.002 


21-23 


0.002 


24-26 


0.002 



Aluminum alloy sheet should for temper No. 1 show 
by tensile 55,000 pounds per square inch, sheet tempered No. 
2, 50,000, the elongation being 2 inches in 15 and 20 inches 
respectively. Strips cut in either direction from either No. 
1 or No. 2 tempered sheets should withstand cold bending 
through an angle of 180°, over a diameter equal to 4 times the 
thickness of the sheet. 

It is to be noted that hammering of sheet aluminum hard- 
ens same and causes it to become very brittle; this is to be 
avoided as much as possible. 

Some parts of aircraft fittings are made from ingot alumi- 
num, or aluminum alloy bars, the alloy bars being made from 
the ingot aluminum which has to be 99 per cent pare alumi- 
num. Ingot aluminum is used in the manufacture of cast- 
ings, aluminum bronze, manganese bronze, etc. The step 
casting on N-9 pontoons is of aluminum alloy. The bracket 
upon which the rudder bar mounts is of the same material. 
Pulleys on land machines are made of aluminum alloy, but 
not on flying boats or seaplanes, the latter being made of high 
grade brass, bronze or canvas bakelite. 



ALUMINUM AND ITS ALLOYS 157 

A good aluminum alloy bar should show by test a tensile 
strength of from 45,000 to 55,000 pounds per square inch: 

1-inch in diameter 55,000 

1^-inch in diameter 50,000 

2-inch in diameter 45,000 



CHAPTER XVIII 

Propeeties and Use of Duralumin 

physical properties 

The outstanding property of duralumin which makes it 
suitable for aircraft work is that it combines strength with 
low specific gravity. 

The following are the general physical properties of 
duralumin: 

Specific gravity 2.80 to 2.85 

Weight 0. 100 to 0. 102 lb. cu. in. 

Melting point 650°C. (1200° F.) 

Coefficient of linear expansion, 

0.0000226 per deg. C. (0.0000126 per deg. F. 

Modulus of elasticity 9,400,000 lb./sq. in. 

Tensile strength 52,000 lb./sq. in. 

Yield point in tension 32,000 lb./sq. in. 

Compressive strength 44,000 lb./sq. in. 

The electrolytic metals negative to duralumin are copper, 
brass, bronze, iron and steel. These metals should never be 
joined to duralumin where subject to moisture. 

Duralumin depends entirely on heat treatment for its re- 
markable physical properties. When annealed by heating 
to a temperature of between 350°C. and 380°C. (660°F. and 
720°F.) and quenching in water or oil, it becomes plastic and 
may be forged or stamped, solid drawn in the form of sections 
or tubes, or rolled into sheets. 

When normalized by heating to about 500°C. (930°F.) and 
quenching in water or oil, the physical properties are very 
similar to those of mild steel, the strength being about 52,000 

158 



PROPERTIES AND USE OF DURALUMIN 159 

pounds per square inch and the elongation 15 per cent in 2 

inches. 

MANUFACTURE 

Tubes and sections under 0.05 inch thick are made by 
solid drawing, thicker tubes and bars by an extrusion process 
like that used for brass and similar alloys. Duralumin may 
be forged and stamped, with a strength after normalizing 
which varies from 48,000 to 56,000 pounds per square inch 
according to the size of the piece. 

HEAT TREATMENT 

Correct heat treatment is essential if the best properties 
of the metal are to be developed to their fullest extent. 

The best method of heating the material uniformly is by 
means of a salt bath. This comprises an iron or steel trough, 
in a brick setting, partly filled with a mixture of potassium 
and sodium nitrates and heated by gas jets. The heat neces- 
sary is greatly reduced if a sheet iron lid protected by a layer 
of asbestos, is lowered over the bath at such times as articles 
are not being placed in or taken out of it. 

Accurate thermometers or pyrometers should be inserted 
in the salt mixture to insure a correct temperature. 

The articles to be heat treated are left in the molten salt 
until they are uniformly heated to the correct temperature 
and are then withdrawn and quenched in water or oil. 

The material is not injured by leaving it in the bath for a 
longer time than is actually necessary, provided that the 
temperature is not allowed to alter. On the other hand, 
ample time should be allowed for the articles to heat through. 

ANNEALING 

Whenever any cold work is to be done on duralumin, it 
must be annealed. If considerable cold work is to be done, 



160 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINE'S 

the material, like brass, must be annealed. between successive 
operations. 

For annealing, the temperature of the bath should be be- 
tween 350°C. and 380°C. (660°F. and 720°F.). The mini- 
mum number of minutes for which the article should be left 
in the bath is 80 times the square root of its least dimension 
in inches, that is, of the thickness in case of a plate, or of the 
diameter in case of a bar. 

At the end of the specified period the article should be 
taken out and immediately quenched, either in water or in oil 
of good quality. 

As the effect of annealing does not last long, any work to 
be done on the annealed parts should be done within an hour 
after annealing. 

NORMALIZING 

For final treatment the material should be uniformly 
heated to 480°C.-490°C. (895°F.-915°F.) and then quenched 
in water or oil. The minumim number of minutes for which 
the article should be left in the bath is 60 times the square 
root of its least dimension in inches. 

After treatment the material remains soft for about an 
hour and then gradually hardens until in about a week the 
full strength is reached. Hence if any test pieces are taken 
from a heat treated article they should not be tested until at 
least a week after treatment. Once hardened, the material 
remains so permanently. 

On account of this property of remaining soft for a time 
after heat treatment and then becoming hard, it is possible to 
straighten while still soft, articles of duralumin which have 
buckled or warped during heat treatment. 

A considerable saving can often be made by working the 
material after final heat treatment. The general rule in this 
respect is that the normalizing temperature should be used 



PROPERTIES AND USE OF DURALUMIN 161 

only when but one operation after heat treatment is required 
to finish the part. If more than one operation is required, 
the annealing temperature should always be used. 

In heat treating duralumin, it is essential that a reliable 
pyrometer be used and that the temperature of the bath be 
earef Lilly watched. If the metal is heated above 550°C. 
(1020°F.) the strength is much reduced and the metal is made 
very hard and brittle. Even when treated between 520°C. 
and 550°C. (970°F. and 1020°F.), the metal becomes some- 
what unreliable. 

HEAT TREATMENT FOR FORGING AND STAMPING 

The material should be heated in a muffle oven to a tem- 
perature of between 380°C. and 420°C. (715°F. and 790°F.), 
and, if possible, a pyrometer should be arranged to read the 
temperature. If a pyrometer is not provided, the correct 
temperature must be found by experience, this temperature 
being such as will brown a piece of ordinary newspaper. The 
forging or stamping should be done as soon as the metal 
leaves the muffle. No definite rule can be given for the time 
when the metal requires reheating, but it soon becomes evi- 
dent when the metal becomes too cold, as it gives a decided 
ring and usually cracks. The final heat treatment for drop 
forgings should always be carried out in the salt bath, in 
order to insure uniform temperature. 

MACHINING DURALUMIN 

The metal can be turned at the same speed as brass. It 
does not seize or drag the tool. Kerosene is a good tool lu- 
bricant in threading or finishing machine parts of duralumin. 



162 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

BEHAVIOR OF DURALUMIN UNDER TEST 

Duralumin has several of what may be called "false yield 
points." As the load is applied the material suddenly yields 
slightly at a low load, but instead of this yield continuing 
the metal remains elastic and finally the true yield point oc- 
curs at a load in the neighborhood of 32,000 pounds per square 
inch. Often several such false yield points occur before the 
true yield point is reached. If the load is removed the yield 
at these lower values remains as a permanent set; if the load 
is reapplied they do not occur again, and the material obeys 
Hooke's law up to the elastic limit. 

DURALUMIN MEMBERS IN TENSION 

Duralumin may be used for any part where a combination 
of strength with extreme lightness is desirable. Where 
small holes are drilled in thin material, a small reduction in 
strength on the material surrounding the holes occurs, this 
being probably due to the heat produced by the drill. 

RIVETED JOINTS IN DURALUMIN 

Rivets should be softened for use at the normalizing tem- 
perature and should be riveted up within one hour of the 
heat treatment. 

The bearing pressure allowed on the rivets should not ex- 
ceed 70,000 pounds per square inch, above this elongation 
of the hole occurs. An ultimate shearing stress of 24,000 
pounds per square inch in single shear may be allowed on the 
rivets. With the very thin plates and members used in air- 
craft construction it is preferable to use a large number of 
small rivets rather than a few large ones. 



PROPERTIES AND USE OF DURALUMIN 163 

DURALUMIN MEMBERS IN COMPRESSION 

As duralumin is a much more reliable material than wood, 



more refinements in reducing weight can be adopted in the 
design of duralumin struts. 

The principal use for duralumin at this time is for the con- 
struction of the frame work in rigid and semi-rigid airships, 
and it is being used to a small extent in heavier-than-air craft. 









CHAPTER XIX 
Overhaul and Alignment of Aircraft 

When the general condition of an airplane, seaplane, or 
flying boat warrants overhaul due to long usage, or having 
become damaged while in use, the following is the procedure 
in connection with overhaul. (1) . Disconnect all piping from 
your engine. Remove engine, and send same to shop for 
overhaul. (2). Remove outer panels. (3). If a seaplane 
of the N-9 or R-6 type or any other type of seaplane with a 
fuselage construction, lift machine from truck by hooking 
crane or chain fall to the lifting cable which is placed in the 
center of gravity in all small machines. After truck has 
been removed, disconnect pontoon struts from fuselage and 
send same to the joiner or wood-working shop if there is any 
work needed on the pontoon. The fuselage is then lowered 
on horses, when the side walk panels, or lower engine sections 
as they are sometimes called, are removed. Then remove the 
engine section panel by disconnecting engine section struts 
from the fuselage. Then remove elevators, rudder, vertical 
stabilizer and horizontal stabilizer. This is followed by the 
removal of the fabric from the fuselage, in order that a care- 
ful inspection may be made of all fittings and wires con- 
nected thereto. This inspection consists of looking for cor- 
roded wires, distorted or broken fittings, the slipping of a 
fitting along the longeron, and a very close examination of 
the longerons themselves, particularly in the wake of pon- 
toon strut connections where the longeron is liable to become 
broken from a hard landing. In the event that a longeron 
is found broken, it will be necessary to remove same and re- 
place with a new one. This means the slackening up of a 

164 



OVERHAUL AND ALIGNMENT 165 

large number of wires and fittings in order that same may be 
removed. It will also be necessary to disconnect all longer- 
ons from the tail post, in order that when the machine is 
aligned that trouble will not be experienced due to one or 
more longerons having taken up more moisture than some 
other. Thus, if the longerons are not disconnected from the 
tail post, in some instances it would be impossible to bring 
the fuselage in proper alignment. 

Having renewed the necessary broken parts, fittings, or 
wires, and cleaned all fittings (which in a majority of cases 
show slight corrosion) by the use of a wire brush, give all 
fittings a coat of red lead paint, allowing same to become 
thoroughly dry, then coat same either with black enamel 
paint or Naval Gray Enamel paint. In the meantime the 
fabric and fittings attached to the wings and tail surfaces is 
carefully gone over to determine its condition, and if the 
wings do not warrant recovering, the same are patched if 
found necessary. Anj T damaged or badly corroded fittings 
are renewed, also control horn brace wires, etc., are carefully 
examined and lenewal made where found necessary. It is 
to be noted that the ribs as well as the veneer on the leading 
edge is frequently found broken, due to someone having 
walked thereon. It is necessary that these be gone over 
carefully in order to determine if they are intact. If such 
is not the case the fabric is opened up and the necessary re- 
pairs made. It is also essential that the tail ribs be examined 
in the vicinity of the metal trailing edge, which due to con- 
densation of moisture, corrodes very rapidly. This condition 
frequently necessitates the removal of the fabric entirely in 
order that steps may be taken to check the corrosion of the 
metal trailing edge. This involves the removal of the fabric, 
which is wrapped around the metal trailing edge, the same 
being scraped and cleaned, then give same a coat of red lead 
paint, allowing same to dry thoroughly; then re-tape, dope, 



166 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

and give the fabric a coat of Naval Gray Enamel paint. 
Where the fabric has been removed in order to carry out the 
preceding work described, the wing panel is then recovered. 
The process and description to be followed in recovering is 
described elsewhere in this work. Naturally, this requires 
the removal of all fittings, which are afterwards replaced 
and refitted, the same having been cleaned, painted, and 
enameled. 

The repairs having been completed to any broken parts 
that may have been found in the fuselage, stranded, badly 
corroded, or broken fittings and wires having been renewed, 
the fuselage is ready for alignment. It is again to be noted 
that the tail post is removed when starting the alignment. 
The fuselage is then placed on its side on two adjustable 
horses. The section of the bottom of the fuselage of the for- 
ward cockpit is "trammeled," or "trammed" diagonally to 
see that this section is square. The cross brace wires are 
tautened so that this section remains square. This operation 
is followed by "tramming" all of the remainder of the bottom 
sections all the way aft to the tail, and then "tramming" for- 
ward, beginning in the section forward of the forward cockpit 
to the nose. The next operation is to start from the after 
cockpit and work aft, "tramming" all sections by means of 
adjusting the center or "X" brace wires. Then "tram" all 
top cross brace wires. Then turn the fuselage on its bottom 
on the adjustable horses. Level the upper longerons of the 
forward cockpit both transversely and longitudinally by 
means of transverse non-flexible strips, straight edge, and 
level. 

The four main struts between the upper and lower longerons 
situated in the forward cockpit, the upper ends of which lean 
forward, to the lower ends of which the hinge fittings are con- 
nected, are then checked for the proper angle. This checking 
is done by dropping a plumb line from center of bolt at top 



OVERHAUL AND ALIGNMENT 167 

of strut, and the distance from the plumb line to the center of 
the hinge at the bottom of the strut, being regulated by 
adjusting the side brace wires in the forward cockpit. In 
an N-9 fuselage this distance should be 4 J inches. This is 
done on both sides of the fuselage, and the brace wires on 
both sides in this section given the proper tension. 

The proper tension for all brace wires is that they be made 
sufficiently taut enough to hold the frame work rigid and in 
place. See that wires are not so taut as to elongate the eyes, 
etc., and that fittings are not imbedded into the wood work, 
and that no part of the frame work is buckled or twisted. 
The forward cockpit having been leveled, as previously de- 
scribed, and the side brace wires in this section adjusted and 
given the proper tension, the next procedure is to shift your 
transverse strips and longitudinal level to the next section in 
the rear of the forward cockpit, and by adjusting the side 
brace wires throughout to the tail, taking one section at the 
time, thus bringing the upper longerons level throughout the 
entire plane. 

The next procedure is to align the two engine bearers. 
This is done as follows: A line is stretched from a portable 
post just forward of the fuselage to another portable post aft 
of the tail, the line being stretched close to the side of the 
fuselage, not touching, and 6f inches below the top of the 
upper longerons which have been previously leveled. It is 
to be noted that this engine bearer alignment to be described 
is to cover the procedure whereby a Hispano-Suiza motor is 
the type of engine being used. The top of the engine bearers 
are brought to the level of the line by means of the brace 
wires. These brace wires enable this leveling to be accom- 
plished transversely and longitudinally. After all of the 
foregoing procedure the fuselage is now lined up, but it is 
essential that the entire alignment be verified, and this pro- 
cedure is as follows: Place a transverse straight edge over 



168 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

and resting thereon the forward end of the engine bearers 
and one at the rear end of the engine bearers, to the center of 
which a plumb line is dropped within 8 or 10 inches of the 
floor or concrete as the case may be, then in the center of the 
transverse braces between the upper longerons at each sec- 
tion as well as through the hinges on the tail post, which has 
been replaced, thus making a long row of plumb lines hanging 
from the forward to the after end of the fuselage, then stretch 
a horizontal line underneath the fuselage and observe care- 
fully to see that all plumb lines just barely touch this longi- 
tudinal line. Any variance must be corrected. This can 
be done by the bottom and top cross brace wires being ad- 
justed so as to pull this section into the line. 

After this has been found correct, all brace wires are safety- 
wired and all nuts and clevis pins are cotter keyed. 

The fuselage is now ready for covering with fabric. After 
the fabric is on, the fuselage is again leveled on the adjust- 
able horses. The leveling of the fuselage at this stage can be 
accomplished only by means of leveling the engine bearers, 
as the longerons are covered with fabric and are more or less 
inaccessible. The fuselage is now in a position for normal 
horizontal flight. 

The horizontal stabilizer is then secured to the tail by "U" 
bolts, which clamp around the upper longerons and around 
the beams of the horizontal stabilizer. A diagonal brace on 
each side of the horizontal stabilizer and underneath is 
secured to lower longeron and to the forward and aft beams 
of the stabilizer. 

The vertical stabilizer is bolted to the horizontal stabilizer. 
Its longitudinal direction is exactly in a fore-and-aft line and 
is pre-determined by the boring of the bolt holes in the hori- 
zontal stabilizer. Its vertical position is adjusted by four 
transverse brace wires which run diagonally down to fittings 
on the horizontal stabilizer. A tram for each side is used in 
this adjustment. 



OVERHAUL AND ALIGNMENT 169 

The rudder is then secured to the vertical stabilizer by four 
hinges. 

The elevators are next secured to horizontal stabilizer, 
there being three hinges to each elevator. 

The upper engine wing panel section is next secured. This 
rests upon four struts which, when secured, form a continua- 
tion of the four main fuselage struts at forward cockpit which 
are not at an angle. 

The lower engine wing panel sections are next secured to 
rhe hinge fittings on each outboard lower side of the forward 
cockpit main struts. The intermediate wing struts, at the 
ends of these panels and connecting the upper and lower 
wings, are then put in place and bolted. The load, lift and 
stagger wires are then connected up and tautened. 

While the riggers are securing these panels the engine crew 
is installing engine on engine bearers. 

To line up wing- panels: (Fuselage in normal horizontal 
flight position on adjustable horses.) Drop four plumb 
lines, one from each end of each upper engine wing panel sec- 
tion at the entering edge, and one from the same entering 
edge just clear of the fuselage on each side. A straight edge 
about 10 feet long is placed on the upper engine wing panel 
section leveled transversely as shown by a spirit level by 
means of adjusting the load and lift wires. The stagger is 
then checked. The entering edge of the upper wing should 
be 9ft inches forward of the entering edge of the lower wing 
on an N-9. This is observed by measuring the distance 
of the plumb line from the entering ed[;e of the lower wing. 
It is corrected or adjusted by means of the "stagger" wires 
between the struts. The angle of incidence of the wings in 
this position of normal horizontal flight is 3| degrees. 

The outboard wing sections are assembled on the floor 
away from the fuselage. The load, lift and stagger wires are 
tautened to hold them rigidly together. The cabane, ailer- 



170 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

ons, control horn and control wires and their leads are all 
connected and secured. 

These outboard wing sections are hung to the center sec- 
tions by means of hinge fittings. The same process of align- 
ing these outboard sections is continued as was used in the 
alignment of the center sections. 

After the alignment of all these wing sections by means of 
the straight edge and level there is still a possibility of their 
being slightly out of alignment. This can be determined by 
sighting along the entering edge of each wing from a position 
near the wing tip to see that a straight line is formed. Sim- 
ilarly for the trailing edge. 

Now stand about 20 feet in front of the center of the 
machine. Bring the entering and the trailing edges of each 
wing in line with the eye and see that no drooping occurs, if 
so, it is to be taken up by the lift, load, and stagger wires. 

As a further check, stretch a wire from the forward center 
part of the forward outboard strut fitting to the center of the 
propeller shaft, measuring this distance on each side to see 
that it is the same. Similarly from the center of the after 
outboard strut fitting to the center of the tail post. 

Connect up all control wires. 

See that ailerons are in line with each other for horizontal 
flight. 

See that elevators are in line with each other. 

Only | inch of play is allowed in all control wires. 

Using a chain fall, raise the machine by hoisting sling, 
place pontoon under it and connect pontoon to fuselage by 
bolting the pontoon struts to it and to the pontoon. The 
pontoon is lined up with the fuselage by the tramming pro- 
cess, tramming the strut sections under the forward cockpit 
first. 

The wing tip pontoons are next secured in place. 

All turn-buckles are then safety-wired, and cotter pins put 



OVERHAUL AND ALIGNMENT 171 

m all bolts, clevis and hinge pins. A careful inspection is 
made for this as it is very important, as one cotter key or 
safety wire left off may cost the pilot his life and wreck the 
machine. 

The machine is then ready for an engine test. 

For the overhaul of flying boats, such as HS-ls, H-16s, 
F-5Ls, or any other type, the procedure is as follows: Remove 
the engine or engines, as the case may be, the outer wing 
panels, tail units, engine sections. Lift the boat from the 
truck by means of jacking, horses provided for the purpose 
being placed under the side walk sections in addition to 
blocking up the hull proper. In this position the necessary 
repairs are made to the hull, and the remainder of the inspec- 
tion and repairs is conducted in the same manner as which 
they were on the N-9 type. 

In connection with the foregoing, careful inspection should 
be made of all control wires, particularly where they, pass 
through Bowden fair leads or around pulleys, or at any place 
where they are liable to create friction and become frayed or 
otherwise damaged, and renew all such wires that are found 
so damaged. A few days before a flying boat is completed, 
particularly those which have been undergoing overhaul for 
some time, it is advisable to put a few inches of fresh water 
into the interior of the boat in order that the bottom may 
take up and be tight from the effects of having become 
shrunk more or less during the period while undergoing over- 
haul or to test out new work. 



CHAPTER XX 
Checking Alignment of Seaplanes on Beach 

Place machine in horizontal flight position (which is level) , 
sight along entering edge of wings from tip to tip, to see that 
same is straight, also trailing edges. 

Get directly behind the machine and sight over the trailing 
edge of horizontal stabilizer to wings to see that both are in 
line laterally. 

Drop plumb lines over entering edges of wings to check 
stagger. By placing yourself about twenty feet in front and 
in center of machine you can check angle of incidence by 
sighting underneath the wings on fittings from fuselage out, 
on both sides. 

To see that wing surfaces are at right angle to fuselage, 
take a steel tape and measure from center of propeller shaft 
to center of outboard forward strut fitting, on both sides, see 
that this distance is equal, also take the distance from center 
of tail post to center of outboard rear strut fitting, see that 
this distance is equal, on both sides. 

Pontoon is lined by tramming brace wires, and taking dis- 
tance with steel tape from center of nose on pontoon to out- 
board forward strut fitting on both sides, and from center of 
tail of pontoon to center of tail post on both sides. 

Sight along trailing edges of elevators to see that both are 
in line; do likewise with ailerons; use all safety precautions 
such as cotter pinning all bolts and safety wiring all turn- 
buckles, seeing that all wires are in proper tension, control 
wires connected up and not allowing over § inch play in same. 

In case of a machine having dihedral angle same can be 
checked by using the dihedral board and level; or by stretch- 

172 



CHECKING ALIGNMENT OF SEAPLANES 173 

ing a line from over the upper wing surfaces from wing tip to 
wing tip directly over the spars or wing beams; and measur- 
ing from spars or wing beams up to line from each section 
or bay, measurements being given on assembly plans of 
machines. 

INSPECTION OF SEAPLANES AFTER FLIGHT 

Check up all alignment (see alignment of seaplanes on 
beach) . 

Inspect all controls to see that they function properly; all 
control wires to see that they are not frayed or strands part- 
ed. This is most likely to happen where they pass around 
pulleys and through fair leads. 

Inspect all fabric-covered surfaces for holes, and also all 
wires such as "Flying," "Load," "Stagger," "Drift," "Land- 
ing," "Pontoon," "Brace," "Fuselage Brace," seeing that 
all are in good condition, properly doped, and in tension. 

Inspect all woodwork where accessible for splits and breaks, 
all fittings to see none are broken or bent, examine carefully 
all hinges of ailerons, rudder, and elevators. 

Inspect pontoon for leaks, etc., clean all parts of machine 
thoroughly, using soap with no alkali in it, as this will injure 
fabric and paint; pure Castile soap is recommended. Use as 
little water as possible, as water will get underneath the 
fabric covered surfaces and injure parts where glue is used, 
as well as cause woodwork to swell and get out of shape. 
Keep all parts free from oil and grease, except where used on 
hinges, controls, etc., as grease will cause the paint to soften 
and come off, and will also cause the fabric and wood to 
decay. 

In connection with the alignment of fuselage type ma- 
chines, in order that the machine may be properly aligned it 
is necessary that the rigger have the assembly plan,which 



174 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

will give him the proper dihedral, stagger, angle of incidence, 
etc., in order that he can align the machine in accordance 
with the dimensions and figures contained thereon. Other- 
wise, the distance between the top of the engine bearers and 
top of the longerons would be unknown, and assembly plan 
is also necessary in assembling a flying boat. The plan is not 
absolutely essential whereby the rigger is familiar with all 
the dimensions required. 

WING HEAVINESS 

Q. How would you correct right or left wing heaviness? 

A. The first procedure would be to find out if the wing 
tip float of the heavy wing was free of water. If no water is 
found therein, then check alignment of the plane. If same 
is found correct it will be necessary to slack all load or lift 
wires on the trailing edge ; slack all stagger wires in the heavy 
wing that lead from the leading edge of the upper wing to the 
trailing edge of the lower wing from J to 1 turn on the turn- 
buckle. Take up a similar amount on the stagger wires that 
lead from the trailing edge of the upper wing to the leading 
edge of the lower wing. This will slightly increase the angle 
of incidence in the upper wing. This is the -only way that 
this condition can be properly corrected. Right or left wing 
heaviness has always been a puzzle to many people in the 
assembly and alignment of aircraft. The cause therefor 
could not be understood. This condition, however, rarely 
ever occurs in any type of machine except flying boats and is 
due to the fact that the side walk beams which pass trans- 
versely through the hull of flying boats are not in all cases at 
absolutely right angles to the boat itself and has a tendency 
to throw one set of wings slightly in advance of the other. 
This, however, can be taken care of by the drift wires, owing 
to the flexibility of the structure. But the principal causes 



CHECKING ALIGNMENT OF SEAPLANES 175 

are that the side walk beams are not in their designed posi- 
tion as to the height from the bottom of the keel; for instance, 
assuming that the flying boat flies with right wing heavy 
and if the outer ends of both right and left wings measure 
the same distance to the bow of the boat, then it is ap- 
parent that the right rear end of side walk beam is high. 
It can readily be seen that the left rear end of side walk beam 
would be low, thus slightly increasing the angle of incidence 
in the left wing and decreasing angle of incidence in the right 
wing, thus causing same to be heavy when plane is in flight. 
This condition can be remedied by slacking and taking up on 
the various wires above mentioned. 






CHAPTER XXI 
Care and Preservation of Aircraft in Storage 

Aircraft in storage in crates are preserved by removing the 
top and one side of all boxes; the windows and doors of build- 
ings should be kept open at least six hours per day every day 
except Sundays, holidays and in inclement weather, and the 
building be kept free of rats or mice. 

Planes that are erected should only be stored when they 
are thoroughly clean in every respect, pontoons drained, 
handhole plates off, all control wires being well greased, load 
and lift and other strand wires being coated with lacquer or 
other preservatives. Remove any corroded spots on fittings 
by the use of a dull knife or scraper and touch up with red 
lead paint. Plane should be in perfect alignment, otherwise 
a condition that should be other than normal would become 
exaggerated. Propeller should be left installed and turned 
to a horizontal position, oil left in tanks. If plane is going 
to be stored for only a short period of time fill all gas tanks to 
capacity, but if stored for an indefinite period gasoline should 
be removed and all gas tanks filled with kerosene. The fill- 
ing of tanks with kerosene only applies to small type craft, it 
being considered impractical to fill flying boat tanks of such 
large capacity with kerosene; in the case of flying boats empty 
all gas tanks. Empty tanks due to changes in temperature 
will set up precipitation, causing tanks to corrode in the in- 
terior and as gasoline evaporates very rapidly it will soon 
leave space for precipitation of moisture. Engines should 
be turned over once a week; buildings should be kept well 
aired daily for at least six hours except holidays, Sundays 
and in inclement weather. In addition to removing drain 

176 



CARE AND PRESERVATION 



177 



plugs in flying boats the interior shall be carefully dried by 
wiping up any water that may lie in places that do not per- 
mit of drainage. High humidity appears to be the greatest 
enemy to erected aircraft in storage, and every effort should 
be made to keep buildings dry and well aired. 

Where it is impractical to remove the top and side of an 
aeroplane crate, such as large type flying boats, an opening 
should be made in each end of crate about two feet square. 
On one end the opening should be made about one foot above 
the floor or bottom side and on the other end the opening 
should be made near the top side. This will permit of cir- 
culation of air. If crates are stored in a building that is 
heated in winter a pan of water should be placed inside the 
crate near the lower opening. If building is not heated, no 
w r ater pan is necessary. 

PARACHUTES IN STORAGE 

Parachutes in storage should not be kept in containers or 
kept folded, but should be suspended in a vertical position 
from the roof trusses of hangar, with the peripheral cords 
downward . Groups of parachutes suspended thus are covered 
with cotton sheeting to keep off dust, dirt, etc. , If building 
has not sufficient pitch to permit of parachutes being sus- 
pended as above described the peripheral cords may be coiled 
upon a table or other elevation, but not upon the floor, the 
fabric of parachutes to be suspended and covered as in the 
first instance. 



CHAPTER XXII 

AlKCRAFT "DonVs" 

1 . Don't endeavor to improve the flying qualities of any fly- 
ing machine by making some change in design or construction 
of same, you may either kill yourself or some other person by 
so doing; remember, the machine will do all it is supposed to 
do, if properly assembled and aligned and motor functioning 
properly; if you have some idea, submit it to the officer in 
charge who will see that it is given due consideration. 

2. Don't set up so tight on load and lift wires that you 
buckle a strut, the maximum amount of resistance to com- 
pression offered by a strut is before being deflected and not 
afterwards, besides there is no occasion for same. 

3. Don't put a seaplane or flying boat up for the night 
without removing drain plugs, and on week ends remove all 
hand hole plates from pontoons as well, in order to ventilate 
same. It is to be remembered that gasoline, oil, and water 
is injurious to varnish, as well as the glue and fabric placed 
between inner and outer layers of planking. 

4. Don't put boat or plane in water until all drain plugs 
are in. 

5. Don't use files on aircraft wires or fittings, nor emery 
cloth or sand paper. 

6. Don't use cotton waste or any kind of waste for clean- 
ing motor or plane. A small piece of waste may get caught 
on some working part of motor, or on a control wire, and 
cause same to jam at a pulley or where same passes through a 
Bowden fair lead; always use cheese cloth. 

7. Don't use salt water soap, or any soap containing free 
alkali, on the fabric; it is injurious to the fabric coatings; 

178 



AIRCRAFT "DONVs" 179 

use castile soap always if possible. A little gasoline might 
be used to remove a considerable amount of grease, but care 
must be exercised because gasoline will remove the fabric 
coatings also. 

8. Don't fly a machine with broken strands in any wires, 
the wires have either become broken through an undue 
strain, or through lack of care have been permitted to cor- 
rode, the latter case being invariably the case with load and 
lift wires, pontoon brace wires, etc. Control wires usually 
become broken or frayed where same passes around pulleys, 
and while the cable itself might not break, due to a small 
number of strands having parted, there exists the danger of 
further fraying in the air, thus causing cable to become 
jammed in pulley housing, and probably causing a plane to 
be wrecked as well as loss of life. 

9. Don't attempt to fly until you have tried out controls. 
It is a very easy matter to get the control wires reversed 
when renewing same ; this has occurred and will cause a flyer 
to nose in. 

10. Don't attempt flight without ascertaining that there 
is sufficient gas, oil, and water, and that the pipes and their 
connections are tight. 

11. Don't attempt flight in a machine that has had a hard 
landing and is apparently O.K., until same has been in- 
spected for broken wires, distorted or broken fittings, align- 
ment checked up. My reason for making the above state- 
ment is as follows: N-9 Seaplanes in particular, upon being 
overhauled have shown distorted and broken fittings where 
pontoon struts connect to fuselage. These same fittings 
have attached to them the fuselage brace wires that are 
located in the engine, gas tank, and forward cock-pit sections, 
and are also found broken or slack due to damaged fittings 
brought about by hard landing. In many cases no one knew 
of this particular condition, as machines were being over- 



180 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

hauled on account of their general condition, long number of 
flying hours, etc. In this connection pilots are cautioned 
when entering a flying machine of the single tractor seaplane 
or land machine, to reach forward on both sides and feel the 
wires to see if they are reasonably taut both in engine, tank, 
and cock-pit sections; it will only take a few seconds, and 
eliminate what I believe to be the non-recovery of some pilots 
when in a left turn or spin. 

Owing to the propeller torque or reaction, whereby the 
fuselage tends to revolve on its axis to the left, which is well 
within the control of the pilot under normal conditions, such 
is not believed to be the case if a hard landing has been made 
whereby the fittings on the right side of forward cock-pit 
were distorted or broken in a hard landing, thus slackening 
these wires perhaps only a small amount, but sufficient to 
cause a slight twist in the fuselage at that point, which is 
amplified more or less in the tail units, thus throwing the 
right side of horizontal stabilizer upwards and the left side 
downwards, thus tending to increase the lift on the right side 
and decrease lift on the left side. This condition is not very 
apt to be noticed unless machine is in such a position where 
same would be conspicuous, which is not the case when stu- 
dents or pilot may return from a flight in which numerous 
landings have been made, when another immediately takes 
his place, goes up, puts machine in right spin, recovers, then 
left spin and can never recover, and is invariably said to be 
lack of experience. This may be true in some cases, but 
from what has been set forth here it is fair to assume that 
such is not so in all cases. 

12. Don't smoke in hangars, nor in any type of aircraft, 
whether on the water, ground, or in the air. 

13. Don't run your motor at full speed, except when being 
tested out after installation in plane and then for only short 
intervals. This applies to machines on the beach and not in 



AIRCRAFT "DONVs" 181 

flight, the results of same will not only overheat the valves 
and other engine parts, but excessive vibration set up thereby 
is not good for the machine as a whole. 

14. Don't enter the rear part of the hull in an HS-l-L type 
of flying boat without removing the hand hole plates for 
ventilation and blowing in hull air taken from a compressed 
air line hose, or ventilated by means of a portable electric 
blower with canvas hose discharge. A person is liable to be 
overcome with gas fumes; this has happened and required 
cutting through the top of hull to rescue the man. 

15. Don't keep oily or greasy rags lying around the han- 
gars; the}' are liable to catch fire through spontaneous com- 
bustion. 

16. Don't walk on the ribs of a wing. If you have to walk 
out on the wing for any purpose be sure and walk on the 
wing beam and be careful with your steps. 

17. Don't fail to keep your control wires well lubricated 
and inspected where they pass around pulleys or through 
Bowden fair leads, also two control wires crossing should not 
rub against each other. 

18. Don't fly with rips or tears in the fabric. Patch same, 
otherwise you run a risk of having a large section of fabric 
torn adrift while in flight, which may cause a serious accident. 

19. Don't walk any and every place on the hull of a flying 
boat — the planking is of light material and will break through 
easily. Use the reinforced places that are provided for the 
purpose. 

20. Don't stand on either side of a propeller in motion, 
as no one can tell when a propeller may fly apart, and observe 
great caution, if necessary to examine motor while running, 
otherwise you run a risk of being seriously or fatally injured 
if struck by a propeller. 

21. Don't attempt to adjust or repair instruments, if same 
are not working properly. Report same to officer-in-charge, 



182 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

who in turn will take the matter up with the Instrument 
Officer. 

22. Don't allow your machine to become dirty and grease 
coated; it is absolutely essential to keep an airplane as clean 
as possible, thus avoiding catching fire, and the machine it- 
self from deteriorating. 

23. Don't fill a gas tank without first having funnel in 
contact with tank and hose fitting in contact with funnel 
otherwise an explosion is liable to take place, being caused 
by a static spark. Stop flow of gas before removing hose or 
funnel. 

24. Don't attempt to correct the tail heaviness of a ma- 
chine, but report same to the officer-in-charge who will have 
someone who understands the reason for same take care of it. 
(Proper method described elsewhere in this book, under 
alignment of Aircraft.) 

25. Don't attempt to correct right or left wing heaviness 
by giving the aileron a droop on the low wing when the other 
aileron is neutral. (Proper method described elsewhere, 
under Alignment of Aircraft.) 

26. Don't fail to know and see that all turnbuckles are 
safety- wired on your machine. 

27. Don't leave off a cotter pin because you might have to 
walk the length of the hangar to get one. 

28. Don't keep leaky or half-filled Pyrenes on the machine; 
remember, when you need them you need them badly. 

29. Don't kick on being furnished galvanized iron wire for 
turnbuckle safety wiring — it is really stronger than copper 
wire. 

30. Don't use a turnbuckle on any wire that shows by 
table to have a less breaking strength than the wire or cable 
itself. 

31. Don't substitute a smaller wire for one being renewed. 

32. Don't use a short barrel turnbuckle on a long wire 






AIRCKAFT a DONVs" 183 

because the table shows it to be as strong as the wire; there 
are both short and long turnbuckles of the same strength, 
and long wires require long turnbuckles. 

33. Don't use a clevis pin of too small a diameter on a 
shackle ; always use the largest clevis pin that you can get to 
go through holes in shackles and you can't go wrong. 

34. Don't ream out holes in fittings or shackles in order to 
get a clevis pin or bolt to go through — you thereby weaken 
same if you do. 

35. Don't bend the tangs on an aircraft fitting to bring 
same to proper angle. If you should be replacing a damaged 
fitting, and the tangs on the new one are not at the proper 
angle, get another, as it evidently is faulty in design; bending 
fittings cold tends to fracture the metal. 

36. Don't put screws in any part of an aircraft whatso- 
ever, without first boring a hole slightly smaller than the 
screw itself; this applies to the very small screws used on cap 
strips where same are fastened to the front and rear wing 
spars, as well as all others. 

37. Don't drive screws in with a hatchet, hammer, or any 
other implement — always use a screw driver. 

38. Don't use wood that shows worm holes in any part of 
an aircraft. 

39. Don't allow the fittings to become corroded on the 
machine; remove the first signs of corrosion with a dull 
pocket knife or a small scraper, and touch up same with red 
lead paint. 

40. Don't allow load and lift wires, pontoon brace, drift, 
wing-tip, float, non-skid, rudder, elevator, stabilizer, aileron 
brace, control wires, or any exposed wires to become cor- 
roded; this can be prevented by the use of Universal lubri- 
cant, or any other wire dope provided for the purpose. 

41. Don't fail to examine frequently the control wires that 
pass through the hulls of flying boats or fuselages in sea- 
planes; they may be rubbing against each other. 



184 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

42. Don't attempt to correct the error if a machine is out 
of alignment in some one place, unless you know just what to 
do, otherwise you are sure to make a bad matter worse. 

43. Don't use Bowden fairlead cable of a length whereby 
the wire passing through same is always concealed, but where 
used the travel of the wire should be sufficient to expose same. 

44. Don't go in the air in any airplane that is going to fly 
over water without a life preserver. Many have lost their 
lives through the lack of same. In other words, the life 
preserver should be worn and not used as a seat or back rest. 






CHAPTER XXIII 

The Air Speed Meter 
functions 

The function of the air speed meter is to register the speed 
of the plane through the air, without reference to its speed 
over the ground. 

Example: A wind is blowing with a velocity of 20 miles 
per hour. We have a plane whose maximum speed is known 
to be 60 miles per hour. If we fly straight into this wind, we 
have 60 minus 20 or 40 miles per hour for our ground speed. 
We turn and fly with the same wind. Then we have 60 
plus 20 or 80 miles per hour for our ground speed. 

Our air speed in both cases will have remained at 60 miles 
per hour, provided the plane has been kept on a level keel 
and the R.P.M. of the motor has been constant. Of what 
advantage is this knowledge to the pilot? 

The airplane derives its lift from the air passing over its 
inclined surfaces. The speed necessary to obtain this lift 
is called "flying speed.'' A loss of this speed is known as a 
stall, or "Compte de Vitesse" as the French say, and results 
in a loss of control over the plane. The control surfaces will 
not respond, due to the resultant decrease in air pressure on 
them and the plane usually falls into a tail spin. 

"Solo" students, due to a lack of experience, are often un- 
able to sense a loss of speed while in flight and are particu- 
larly liable to this sort of trouble. 

The air speed meter shows the pilot at all times whether 
or not a safe margin of flying speed is being maintained, re- 
gardless of the direction of movement of the body of air 
through which he is flying. It forewarns the pilot when the 

185 



186 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

plane is approaching a stall; shows correct speed when glid- 
ing, and when diving the plane; enables him to know when 
the highest velocity has been attained, from which he can 
make a safe recovery — this varying with the structural 
strength of different types of planes. 

The air speed meter has been found to be particularly in- 
dispensable on the larger types of aircraft such as the Hand- 
ley-Page land planes or the N-C types of flying boats where 
the mass is so great that the pilot can not depend upon "feel" 
of the craft. 

DESCRIPTION 

The air speed meter assembly is composed of three main 
parts: 

The "nozzle," or "venturi tube" 

The "gauge" proper 

The copper tubing and the flexible connections. 

We will first give our attention to the gauge, which is an 
instrument of the diaphragm type. An air tight cylindrical 
case, usual! of aluminum, contains the mechanism. Flexible 
metallic bellows of very light construction and of sensitive 
action are directly connected to the "static" tube leading 
from the case to the "static" tube of the nozzle. A suction 
head is produced by the air stream passing through the 
"static" tube of the nozzle which acts, upon the inside of the 
bellows or diaphragm. A pressure head is produced in the 
"impact" chamber of the nozzle by the "impact" of the air 
stream which transmitted through the pressure tube to the 
inside of the air tight case acts upon the outside of the 
bellows. 

The elasticity of the bellows resists the combined action of 
the two atmospheres, pressure and suction, and the result is a 
distension of the diaphragm. This slight action is multiplied 
through levers, and transmitted through a segment to a 



PLATE 1 



MOLE FOR DIAL. SCREW 



ADJUSTING- LINK 




AIR. SPEED METER A55EM&LY 



PLATE 2 




A -IMPACT TUBE 

B — STATIC TUBE 

G- EXTERNAL NIPPLES 

C?— BASE PLATE 

E— STANPARP COUPLINGt 



VENTURl NOZZLE 



S CORNER OF PLATE 




THE AIR SPEED METER 187 

pinion which carries the hand as shown in plate 2 of the illus- 
tration. 

A double hairspring provides a return action for the hand. 
Dials for air speed meters are graduated in knots or nautical 
miles per hour usually from 30 to 140 knots according to the 
speed of the plane for which it was designed. Both hand and 
dial are suitably illuminated by the use of luminous paint. 

A rubber gasket provides an air tight cushion for the glass 
which is of double thickness and is held securely in position 
by a threaded bezel. An extended flange is drilled with 
holes for screws for securing the instrument in place on the 
instrument board. 

THE "NOZZLE" OR "VENTURI TUBE" 

By consulting plate 3 of our illustration, we see that the 
nozzle consists of a single throat "venturi tube" and a small 
impact tube both of which, when installed on the plane, point 
into the wind at the normal angle of flight. 

The prevailing practice has been to manufacture these 
tubes of aluminum but due to the chemical action in the tube 
caused by salt water spray in the case of seaplanes and other 
hydro-aircraft, aluminum is being discontinued in favor of 
copper. Any deposit or roughness in the tube will affect the 
readings materially. A variation of toVo of an inch in the 
bore of the tube being sufficient to cause an error of 2 to 4 
knots in the reading on the dial. 

The two tubes form one casting with a flanged base for 
attaching to the strut. Two external nipples serve to connect 
the tubes leading from the nozzle to the pressure gauge tube. 

The characteristics of the tube are such that at a speed of 
100 knots per hour, the difference in pressure between "P" 
and "S" is 42 inches of water. At other speeds the variation 
of the pressure head is directly proportional to the square of 
the velocity. 



188 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

TUBES AND CONNECTIONS 

The tubes for connecting the nozzle to the air speed meter 
are of copper \ inch in diameter. The couplings are made by 
means of heavy rubber tubing carefully shellacked to insure 
against any possible leakage. One is usually placed at the 
lowest point in the line to facilitate drainage should any mois- 
ture condense in the tubes. 

INSTALLATION 

The mounting of the air speed meter differs slightly with 
different types of planes, but in every case the nozzle is so 
placed that it will not be affected by the air stream from the 
propeller or by the eddy currents set up by some part of the 
structure. 

On hydro-aircraft the nozzle is mounted well up on the 
strut to avoid as much spray as possible in "taking off" and 
landing. Plate 2 shows clearly the conventional position 
for mounting the nozzle on the forward strut of the outer 
wing section. 

Great care should be exercised when securing the nozzle to 
the strut, to avoid cutting away or drilling holes in the wood, 
or any other alterations that could possibly lower the factor 
of safety of the strut. It will be noticed that the nozzle 
slopes downward from its base at an angle to prevent rain 
or other moisture from entering the tubes. All connections 
between the nozzle and air speed meter must be air tight and 
there must be no sharp bends nor kinks in the copper tubing. 

The location of the instrument on the instrument board 
in the cockpit of the machine is relatively of little importance, 
the principal object being to have it easily visible to the 
pilot. 



THE AIR SPEED METER 189 

TROUBLES 

When an air speed meter fails to register correctly, it is 
usually due to one of the following causes as given below 
with the corrections for each: 

(a) Air leak at connections 

(b) Split in copper tubing 

(c) Hole in case of instrument from corrosion or other 

cause 

(d) Crack in glass 

(e) Leak at rubber gasket due to hardening or deter- 

ioration. 

(f) Hand loose on pinion. 

(g) Water collected in tubes. 

(h) Nozzle set at an angle to the line of flight. 

THE AIR SPEED METER 

Corrections: 

(a) Renew rubber connections and shellac carefully. 

(b) Replace tubing or solder if convenient. 

(c) Remove mechanism from case, ream out hole and 

fit with plug of same material as the case. 

(d) Replace glass. 

(e) Renew rubber gasket if possible or coat with or- 

dinary tire cement and replace glass in position. 

(f) Close hole slightly, using a ball-faced punch in 

the staking tool. 

(g) Drain the line thoroughly at the lowest point by 

removing connections. 
(h) Raise the tail of the plane until the wings are at 
the angle of normal flight, then check position 
of the nozzle to see that it is just horizontal. 



190 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

CALIBRATION 

As before stated, the markings of a dial of an air speed 
meter in knots are equivalent to the indication on that 
gauge of a certain pressure which corresponds to the speed of 
air by the nozzle. Therefore, in order to test the gauge, a 
manometer is necessary and the manometer and the gauge 
connected in parallel. A hand bulb is used to produce the 
necessary pressure. A scale can be had for use in connection 
with manometer, reading correctly in knots and pressures in 
inches of water. 

By simply increasing the pressure, it can be determined 
whether or not the gauge reading corresponds to the reading 
of the water manometer which is the standard. Attention 
is called to the fact that the gauge must be connected on the 
tube marked "pressure," or it will read in a reversed direction 
and be injured. 

The instrument shall always be handled with the utmost 
care as shocks are detrimental and under no condition should 
the instrument be blown into. 

In view of the cost of the apparatus needed and the ex- 
perience necessary for re-calibration of air speed meters, we 
recommend that the instrument be sent to an aero laboratory 
to insure the best results. 

TEST OF THE NOZZLE 

The nozzle is tested by taking the plane over a measured 
course, it having been previously determined that the gauge 
is correct and all connections tight. Should the reading then 
be incorrect, the position of the nozzle with respect to the 
plane should be checked, and if everything is found to be in 
order the nozzle should be deemed defective and should be 
returned to the makers. 



THE AIR SPEED METER 191 

A nozzle will be considered satisfactory if the reading of 
the air speed meter corresponds to the actual speed over a 
measured course within 2 per cent. To obtain very accurate 
timing a still day should be chosen for speed trials. If the 
wind is blowing, the usual methods of allowing for drift 
should be exercised, but it is reasonable to expect that the air 
speed meter may not check quite so closely as on a test under 
more favorable conditions. 



CHAPTER XXIV 

The Altimeter 
functions 

The altimeter is an instrument mounted on an aircraft to 
show continuously its height above the surface of the earth 
from the point from which it started. This point must be 
kept in mind when flying near mountains. When flying 
through clouds or a heavy fog at low altitudes, the altimeter 
is a decided necessity. 

There is considerable lag in even the most improved types 
of altimeters, while climbing this lag is of little concern as the 
rate of ascent is comparatively slow, but when gliding down 
the loss of altitude is comparatively rapid and the instru- 
ment may not register this loss as rapidly as it actually takes 
place. Accidents have occurred from this cause alone when 
landing in heavy fogs. 

The altimeter is always set to register zero at the ground 
level of the starting point. 

DESCRIPTION 

A cylindrical case of aluminum similar to the case of the air 
speed meter contains the mechanism; it has an air vent in the 
case so that the atmospheric pressure at various altitudes 
inside and outside the case will be equalized. 

The mechanism consists of a corrugated, hollow disk made 
of resilient metal from which the air has been exhausted, 
commonly known as an aneroid disk. Two studs are fas- 
tened in the center of this disk on opposite sides. The lower 
stud is secured to the base plate, the upper to a stiff curved 

192 



PLATE 3 




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THE ALTIMETER 193 

spring. The disk is thus held in tension between the base 
plate and the mainspring. 

A bimetallic compensating bar connects the spring to a set 
of right angle multiplying levers as shown in plate 3. The 
final transmission of movement to the hand is obtained by 
means of a chain such as may be found in English w T atches 
of. the "fusee" type. On older types of altimeters, horse 
hair or fine catgut is sometimes used in place of a chain 
but both are unsatisfactory due to the effect of moisture on 
them. 

A collet on the center staff acts as a drum for the rolling 
and unrolling of the chain, a hairspring provides a return 
action for the hand. 

The dial is secured to a movable milled bezel which is 
turned when setting the altimeter to zero before starting on 
a flight. Thus the hand remains stationary and the zero on 
the dial is moved to coincide with the hand. A locking de- 
vice holds the bezel securely in place when set and prevents 
the vibration of the plane from turning the dial in error. 

Dials for altimeters are calibrated in feet from zero to the 
capacity of the instrument in hundreds and thousands of 
feet. Various types range from 10,000 to 20,000 feet maxi- 
mum depending on the work for which they are intended. 
Numerals and hands are illuminated on modern types bj' 
use of luminous paint. 

PRINCIPLES INVOLVED 

For every given altitude there is a corresponding decrease 
in atmospheric pressure. 

The aneroid disk containing a partial vacuum is partially 
collapsed against the tension of the mainspring by the normal 
atmospheric pressure at sea level. As the aircraft gains 
altitude, the decreasing atmospheric pressure allows the disk 



194 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

to expand in like proportion. This slight action is trans- 
mitted from the mainspring through the compensating bar 
to the multiplying lever, through chain to center staff which 
carries the hand. In descending, the action is reversed. 

It is well to bear in mind that pressure decreases as alti- 
tude increases, in spite of the fact that the reading in feet is 
higher. There are other conditions beside pressure which 
affect an altimeter; namely, temperature of the air, and vi- 
bration of the machine. 

The altimeter is compensated for any change affecting 
the instrument itself, ranging from below to over 100°, but 
no satisfactory way has yet been discovered for compensat- 
ing for the changes in temperature of the atmosphere itself. 

TROUBLES 

Altimeter troubles can easily be traced to one of the fol- 
lowing causes: 

(a) Plugged air vent 

(b) Loose hand 

(c) Bent center staff 

(d) Chain rusted 

(e) Hair spring rusted 

(f) Bearings gummed 

(g) Diaphragm fatigued 
(h) Off calibration 

Corrections: 

(a) Remove hand and dial, and open vent with a steel 
broach using care not to enlarge it beyond its 
original diameter. Never insert broach with 
out first having removed the dial in order to 
avoid injury to any part of the mechanism. 
Make sure that no particle of foreign substance 
from broaching remains in the case. 



THE ALTIMETER 195 

(b) Remove hand with proper hand remover and 

close brass cup in center on a staking tool. 
Avoid touching luminous paint with the fingers 
or cracking it during the operation. 

(c) Release chain from lever and remove the bridge 

supporting the center staff, hairspring and col- 
let. Remove the brass chain, collet and the 
hairspring; place center staff in a lathe between 
centers and true. It will seldom be found neces- 
sary to anneal the staff during this operation. 

(d) If badly rusted, replacement with a new chain is 

advised, otherwise a thorough cleaning and 
oiling may be sufficient. 

(e) Renewal is always advised in cases of rusty hair- 

springs. 

(f) A thorough cleaning and oiling, using the same 

general methods as used in cleaning French 
clocks, will remove this trouble. 

(g) In this case the diaphragm has lost its elasticity 

and a replacement is the only solution of the 

difficulty, 
(h) The apparatus necessary for the calibration of an 

altimeter is simply a bell jar and suction pump 

as shown in plate 4. 
An altimeter whose calibration is known to be correct is 
placed under the bell-jar with the instrument to be tested; 
the air is gradually exhausted from the bell-jar by means of 
the suction pump and the difference in readings noted. Ad- 
justment is obtained by turning the adjusting screw on the 
right angle levers which simply increases or decreases the 
motion, as the case may be. 

Due to the fact that the interior of the altimeter case is 
connected to the outer air via the vent, we find it subject to 
more or less trouble from corrosion and rust in the mechanism 



196 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

and consequently in need of frequent attention. This is 
particularly true when the instrument is installed on water 
craft. 

The altimeter is mounted in a hole on the instrument board 
according to the blueprints of the particular type of the 
machine for which it is intended. 

Care should always be used to keep the small vent at the 
base of the instrument clear. It has been found advanta- 
geous in some types of planes to support the altimeter in a 
ring of live rubber which of course absorbs a great deal of 
vibration and insulates the instrument to some extent from 
shocks. 

The latest types of altimeters have a diameter of 3J inches 
and in some cases have the capacity up to 30,000 feet, which 
will be increased as the " ceiling" of aircraft grows higher. 



PLATE 4 




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PLATE 5 




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CHAPTER XXV 
The Recording Barograph 

The recording barograph is a member of the altimeter 
family, recording graphically on a chart the course taken by 
an aircraft in flight, in time elapsed and in altitude made. 

The charts used for these records are graduated vertically 
in feet, and horizontally in hours and minutes. 

By means of the recording barograph, the pilot, after the 
completion of the flight, may follow his up and down course 
through the air, know the time consumed in reaching any 
altitude he may have made, and also make comparisons of 
climbing and gliding speeds. He can also note his exact 
altitude for any minute of his flight. A great deal of interest- 
ing and instructive information may be deducted from a fin- 
ished chart. Plats 5 shows clearly a chart with the con- 
tour of a rather interesting aerial voyage., 

The barograph is sometimes used to check the skill of the 
pupil in carrying out orders to fly over a given course at a 
given altitude. A steady climb is indicated by a steady line 
but if the line on the chart is full of jerks or sharp angles, it 
shows that the rate of climb was uneven. 

Official altitude tests are always verified by the use of a 
sealed recording barograph. 

DESCRIPTION 

The mechanism consists of three principal parts all mount- 
ed on a common base; the clock work and chart drum, the 
tracing pen, the aneroid and connecting levers. 

In the best practice, the clock work is contained in the 

197 



198 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

drum which revolves around it, and the chart is secured tight- 
ly around the cylinder by suitable clips or lugs. As the drum 
revolves the pen draws an actual curve of altitude against 
time on the chart. The pen which is located at the end of a 
long arm or spring is similar to the point of a drafting pen 
and has a recess or well for holding the special glycerine ink 
which is furnished with the instrument. An adjustable 
steady post serves to hold the pen against the paper chart at 
an even tension. The arm holding the pen is directly con- 
nected to the fulcrum bar of the right angle lever which is in 
turn connected to the aneroid. 

On account of the action required to produce the motion of 
the pen against the revolving chart, two or more aneroid 
disks are used, held in tension between the base plate and 
spring much the same as in the altimeter, also a more sensi- 
tive action is obtained by the use of the additional disks. 

The bearings of the levers and fulcrum bars are hardened 
and pointed pivots, supported by suitable "Vee" bearings 
which are adjustable. Accurate fitting at these points is 
imperative as any loss of motion here would greatly impair 
the action between the aneroid and the point of the pen. 

A hinged cover protects the entire mechanism and is pro- 
vided with means for locking and sealing as may be required 
for tests. A small observation window directly over the 
chart enables the pilot to take readings while in flight. 

The pocket barograph is simply a smaller and more com- 
pact edition of the larger one. The principal difference being 
in the means for holding the chart, which travels under ten- 
sion over two rollers instead of revolving on a single drum. 



THE RECORDING BAROGRAPH 199 

TROUBLES 

The usual troubles in their order are given below: 

(a) Improper consistency of the ink. 

(b) Failure of pen to feed. 

(c) Roughing of surface of the chart. 

(d) Error in altitude reading. 

(e) Error in time reading. 

(f) Stoppages. 
Corrections . 

(a) A special ink is required that must be of proper 

viscosity, neither too thick, which results in a 
failure to flow; nor too thin which means a 
smeared chart and empty pen. Ink should be 
tested in an ordinary ruling pen, such as drafts- 
men use before filling the pen on the Barograph. 

(b) Failure of the pen to feed is usually due to one of 

two things, the points set too close or the steady 
post usually results in a failure to feed at high 
altitudes, as the angle of error increases toward 
the top of the steady post. Straighten post 
until pen touches at all points from bottom to 
top. 

(c) Usually two causes; pen point too sharp or burred, 

chart paper of poor quality. 
Smooth point by careful dressing on fine oil 

stone. 
Renew the supply of charts and see that paper 

is of good quality, smooth surface and firm. 

(d) Check calibration by test under bell-jar using 

same methods as for calibrating the altimeter. 
Inspect all bearings for loss of motion. Make 
sure the pen is operating smoothly in the ver- 
tical. 



200 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

(e) Inspect movement- of clock work for possible 

causes of intermitting stoppage. See that 
chart fits drum closely and does not slip. Clock 
work must be regulated correctly for time keep- 
ing. 

(f) Inspect driving gears between clock work and 

drum for possible obstructions such as bits of 
paper or other foreign matter as might cause a 
stoppage. Make sure that clock is in first class 
running condition. 
A careful study of the plate 6 should give the reader a 
thorough knowledge of the instrument. 



CHfi\fZT HOLDER 



PLATE 







PRIVIN& GEAR 



ADJUSTABLE 

6TEAPY fOST 



RECORPINq- BAROGRAPH 



CHAPTER XXVI 

The Tachometer 
the tachometer or revolution counter 

One of the most accurate and dependable checks on engine 
performance for the airplane is obtained by means of the 
tachometer which shows on a dial the revolutions per minute 
of the engine. 

The pilot may be an expert on aircraft engines and be able 
to tell from the sound of an engine a great deal about its 
performance, but after a short time in the air with the motor 
running "full out" the hearing is more or less impaired by 
the changing of atmospheric pressure and the roaring of 
the exhaust so that in the end the tachometer is the real 
source of information. 

The tachometer is driven off the crankshaft, the camshaft, 
or pump shaft of the engine depending on the type. A suit- 
able adapter is used and a correct gear ratio interposed be- 
tween the shaft on the engine and the flexible shaft of the 
indicator. The dial is calibrated according to the speed at 
which the engine runs, usually from 200 R. P. M. to 2400 
R. P. M. which covers the field of aircraft engines. 

Some tachometers have a recording device and much like 
those used on speedometers for motor cars, but on later types 
this has been discontinued, as the limited use for a device of 
this kind did not warrant its cost. 

DESCRIPTION 

The tachometer unit may be divided into three parts: 
the tachometer head, the flexible drive shaft, and the adapter. 

201 



202 AIRPLANES, AIRSHIPS, 

The usual adapter consists of a set of double gears inclosed 
in a swivel housing, of proper gear ratio for the engine and 
tachometer speeds. (See plate 7.) The flexible shaft is 
similar to those used in automobile practice for driving 
speedometers. 

We shall be chiefly concerned with the tachometer head 
and a careful study of the text and plates should make the 
reader entirely familiar with it. The mechanism is inclosed 
in a case of 4J inches in diameter, usually of pressed steel as 
the working parts of this instrument are subjected to more 
strain and vibration than any other instrument on the air- 
plane. A number of different types are manufactured, but 
the centrifugal type using a flyball governor seems to pre- 
dominate. (See plate 7.) 

A ring governor was used in early efforts by some European 
makers consisting of a ring pivoted at the center and held in 
a plane inclined to a horizontal by a spring action. Upon 
rotating, centrifugal force would tend to make it assume a 
horizontal position. The objection to this type being that in 
starting and at low speeds the governor was badly out of run- 
ning balance causing excessive vibration and surging. 

Electric types are still in use by the French but owing to 
cost, weight and the difficulty of keeping them calibrated 
while in service they have not proved generally satisfactory. 

A chronometric tachometer of the escapement type is now 
being manufactured in this country and is extremely ac- 
curate. Error 3 are not cumulative as in centrifugal types 
due to automatic correction every half second. A fine tooth 
gear driven from the main shaft at a speed proportional to 
the R. P. M. of the engine engages a rack or counter which is 
in turn connected to the escapement mechanism. The 
function of the escapement is to hold the counter in connec- 
tion with the driving pinion for a definite period usually one- 
half second. This period of time is constant regardless of 



PLATE 7 



BALL BEARING- 



UPPER BRICG-E 



CENTER. PINION. 
■STAFF & HAIRSPRING 




APJU5TABLE FINGER 
RUNNING IN GROOVE 



TACHOMETER 



THE TACHOMETER 203 

the R. P. M. of the driving pinion. The angle through which 
the gear is rotated in the half second of time it is in mesh is 
proportional to the speed of the engine. The motion of the 
counter is transmitted through levers into a proportional 
angular rotation of the hand on the dial. Power for driving 
the escapement is derived from a mainspring which is wound 
automatically and contained in a barrel similar to those found 
in watches. The inner end of the spring is connected to an 
arbor, the outer end being free to rotate within the barrel. 
When sufficient speed has been attained, the free end of the 
spring will slip around the inside of the barrel the speed of 
which will remain practically constant, the pressure exerted 
by the spring on the inside of the barrel being sufficient to 
drive the escapement. 

The one possible objection to this type is the fact that it 
does not register the speed variation at the instant it occurs, 
it being necessary to wait a full counting period before any 
variation is shown. Thus, the hand of the instrument ap- 
pears to have a somewhat erratic and jerky action during the 
periods of change in the R. P. M. of the motor. 

We will now take up in detail the construction of the cen- 
trifugal type. A heavy brass plate forms a base on which is 
mounted two bridges forming supports for the ball-bearings 
upon which the main shaft rotates. A governor of the fly- 
ball type is mounted on the shaft and acts directly against 
the tension of a coil spring. A flexible coupling at the lower 
end of the shaft provides a means of connection to the flexible 
driving shaft. 

A grooved ring integral with the lower part of the governor 
transmits the action of the governor through a hardened 
steel finger riding in this groove to a pivoted bar carrying a 
segment. The segment engages a pinion on the center staff 
which carries the hand. A hairspring provides the return 



204 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

action for the hand. Two adjusting screws limit the motion 
of the segment bar and make calibration of the instrument 
comparatively simple. 

TROUBLES 

(a) Broken connections in drive shaft. 

(b) Loose hand. 

(c) Surging. 

(d) Vibrating of hand. 

(e) Sticking of hand. 
(i) Off calibration. 

Corrections: 

(a) Replace pins which may be sheared off. 

(b) Use same method for tightening as given for alti- 

meter hand. 

(c) Surging is caused by the governor being out of 

balance. A careful checking of all its com- 
ponent parts will usually reveal a bent member 
as the cause of the trouble. 

(d) Insufficient tension of the hairspring. 
Lack of lubrication on moving parts. 

(e) Burrs on moving parts or oil which has gummed. 

(f) The apparatus necessary for calibrating tacho- 

meters is shown in plate 8, and consists of an 
electric motor equipped with a resistance for 
variable speeds and a coupling for tachometer 
drive shaft. 

The tachometer to be tested may be checked against 
another tachometer whose calibration is known to be correct 
or by means of an ordinary speed counter and stop watch. 



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THE TACHOMETER 205 

The corrections as before mentioned are made by means 
of two adjusting screws on the segment arm of the 
instrument. 

Dials and hands on the later models are luminous and a 
heavy threaded bezel holding the glass completes the case 
assembly. 



CHAPTER XXVII 

The Aero Compass 

With the development of aircraft having a large radius of 
action has grown the demand for instruments for aerial navi- 
gation and the most important of these is the aero compass. 
(Although the gyro compass is in many respects ideal, up to 
the present time its weight and bulk have precluded its use 
for aerial work) . 

The compass now in general use on aircraft, and the com- 
pass we will study, is of the vertical magnetic type. As 
shown in plate 9, the aero compass consists of a heavy glass 
bowl mounted in a suitable frame work of some non -mag- 
netic material, which is provided with brackets for installa- 
tion in the plane. 

The compass proper is insulated from shocks and vibra- 
tion by rubber pads or a cushion made of horse hair. The 
compass card is mounted on a jewel pivot and may be read 
either from the top or from the edge. The card floats in a 
mixture of alcohol and distilled water to damp vibration. 
The needles or bundle of needles is fastened to the under side 
of the compass card. 

When not affected by local magnetic influences, the needle 
will point to magnetic north. On an airplane, there are, 
however, almost always other influences which distract the 
needle from magnetic north. This error is called deviation, 
and is corrected by the use of compensating magnets placed 
on the side or below the compass, running fore and aft and 
athwartship. 

The main thing to realize about the compass is that as a 
navigating instrument it is worse than useless if not properly 

206 



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AERO COMPASS 



THE AERO COMPASS 207 

installed and compensated for the errors. This cannot be 
accomplished until it is well understood and appreciated how 
easily a compass may be affected. Every time the machine 
undergoes any changes such as motors, gas tanks, or other 
metal equipment, the compass must be compensated. A 
severe shock or a change from one latitude to another will 
often affect the deviation. 

COMPENSATION 

To compensate a compass in a machine, the following in- 
structions should be carefully observed: 

1 . Be sure to have all the equipment aboard, such as tools, 
spare parts, or other metal bodies which are a part of the 
regular equipment of the planes. 

2. By means of a standard compass establish a north and 
south line. Likewise establish an east and west line. These 
lines may be either on the ground or on a range. 

3. Level the machine carefully and make sure there is no 
magnetic material in the vicinity. 

4. Head the plane due north and note the arrow in the 
compass reading. Correct this error by inserting or remov- 
ing, as the case may be, the necessary athwartship magnets. 

5. Head the plane due east and correct as before using the 
fore and aft magnets. These correcting magnets are usually 
small bars of soft iron heavily magnetized and are supplied 
by the manufacturers for the compass. 

The period of a compass should be from 14 to 18 seconds; 
that is the time it takes to make one complete oscillation. 
Suppose we draw the needle east by means of a magnet. 
Then remove the magnet quickly and start a stop watch as 
the needle passes north going west and stop the watch when 
it passes north going west, and stop the watch when it passes 
north going west for the second time. Another way is to 



208 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

take one-half of an oscillation. Start the stop watch as the 
needle passes north going west and stop it as the needle passes 
north going east. 

To determine whether a compass is over sensitive or slug- 
gish, count the oscillation it makes before coming to a dead 
rest. 

A common source of trouble arises from a bubble forming 
in the compass. To correct this, unscrew the vent plug and 
fill with a mixture of distilled water and alcohol, by means of 
a common dropper. Connected to the side of the bowl is an 
expansion chamber made of thin metal to allow for expansion 
of the liquid due to changes in temperature. 

Sometimes vibration will cause a compass card to spin and 
this may be usually traced to a badly mounted card or dam- 
aged pivot. 

Directive force is the horizontal component of the earth's 
magnetic attraction. When a compass is sluggish in getting 
back to north, it is said to lack directive force. This may be 
due to some inherent bad quality of the compass or the pivot 
and pivot bearing may be rough. In jewel bearings a cracked 
jewel is a frequent source of this trouble. 

In the modern types of compasses the numerals of the 
cards are luminous and the liquid slightly tinted to empha- 
size the markings. 



CHAPTER XXVIII 

The Temperature Gauge 

The distance type temperature gauge enables the pilot to 
read on a dial located on the instrument board the tempera- 
ture in degrees Fahrenheit of the water in the cooling system 
and also of the lubricating oil in the sump of the engine. 
This gives a timely warning of over heating and its resultant 
injuries to the power plant. 

Oil and water temperature gauges are identical and inter- 
changeable, usual types reading from 100° to 212°F. Some 
later models, however, are designed to read as low as 32° 
although this type of instrument is more delicate and is not 
so reliable as the first type mentioned. 

The instrument consists of three main parts: 

(1) The bulb containing the liquid. 

(2) The capillary, or tube connecting bulb to gauge 

(3) The gauge proper. 

There are two general types in use at the present time, the 
vapor pressure and the liquid filled. The bulb containing 
the liquid is made of steel having a high tensile strength in 
order to withstand the high pressure necessary. A special 
male bushing, or nut, is provided for the attachment of the 
tube to the radiator or to the engine base. The tube is made 
of heavy copper with a hole of very small diameter and all 
connections brazed. 

The gauge as shown in plate 10, is much like an ordinary 
pressure gauge consisting of a fight Bourden tube, suitable 
connecting levers to a segment and pinion which carries the 
hand as described in detail in the lecture on Pressure Gauges. 
The dial is illuminated by the use of luminous paint and is 

209 



210 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

calibrated in degrees Fahrenheit instead of in pounds per 
inch. 

Having extracted all the air from the bulb capillary and 
Bourden tube in the instrument, ethyl ether is introduced 
into the bulb under a pressure of 400 and 500 pounds per 
square inch. The tube is then sealed up. Ether is liquid 
at room temperature. The bulb, therefore, contains liquid 
ether in contact with other vapor in the tube and spring. 
A definite pressure results for every given temperature in- 
dependent of the volume of the container. 

The higher the temperature the higher the pressure. 

This pressure is an accurate measure of bulb temperature 
and is utilized to operate the Bourden tube of the pressure 
gauge. The pressure measured is of course a difference be- 
tween vapor and atmospheric pressure. As the atmospheric 
pressure changes due to altitude, an error is introduced but 
excepting at extremely high altitudes this error is not suffi- 
cient to destroy the required accuracy of the instrument. 

In instruments designed to record the lower range of tem- 
peratures, a liquid having a lower boiling point is employed. 
The two liquids now commonly used are sulphur dioxide and 
methyl chloride. There is some objection to the use of sul- 
phur dioxide on the grounds that some impurity in the liquid 
might cause it to attack the metal with which it comes in 
contact. The liquid used must be of such a nature that it 
will not attack or amalgamate with the bulb and tubing 
materials. This precludes the use of mercury which is the 
standard in stationary practice. 

THE LIQUID FILLED TYPE 

The liquid filled type registers from 32° to 212°F. The 
liquid is introduced into the bulb and capillary under pressure 
of 1000 pounds to the square inch. The capillary communi- 
cates with a coiled tube in the instrument, one end of which 



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THE TEMPERATURE GAUGE 211 

is fixed while the other carries a compensating spring. The 
free end of the compensating spring carries the pointer. 
The increase of temperature in the bulb causes the liquid to 
expand and forces it into the coiled tube which tends to un- 
coil moving the pointer with it. In case the instrument is 
cooled considerably as at high altitudes the liquid in the 
coiled tube would contract and would cause the thermometer 
to read low, but the effect of the lower temperature on the 
compensating spring causes it to coil in the opposite direc- 
tion, thus compensating for the error in the gauge so that it 
still indicates accurately the temperature in the bulb. 

The diameter of the capillary is so small that the quantity 
of liquid contained, and therefore its effect on the reading, is 
negligible. 

The greatest source of trouble in these gauges is the break- 
ing of the tube. This is usually the result of careless hand- 
ling by mechanics or from poor installation in the plane. As 
the refilling of these tubes is a most delicate operation requir- 
ing special equipment, we advise that in case of breakage 
they be returned to the manufacturer. 

CALIBRATION 

The apparatus for recalibrating temperature gauges as 
shown in plate 11 consists of an electrically heated bath and 
a standard mercury thermometer. The bulb of the in- 
strument to be tested is submerged in the water which is 
gradually heated and the results in temperature checked 
against the standard thermometer. 

Adjustment is obtained by means of a screw on the con- 
necting arm of the segment which increases or decreases the 
motion of the pointer in relation to the spring action as may 
be needed to properly calibrate the gauge. 



CHAPTER XXIX 

The Pressure Gauge 

The mechanism of the pressure gauge for either air or oil, 
is very simple and consists of only six parts, namely: A 
Bourden tube, connecting links, segment^ pinion, center 
staff, and hair spring. 

The Bourden tube is a flat, hollow, curved spring. 

If the gauge is registering the oil pressure, it is directly 
connected to the oil line from oil pump. The oil goes into 
the Bourden tube and its pressure tends to straighten it out, 
the action being carried by the connecting links to the seg- 
ment which is in mesh with the pinion gear on the center 
staff, causing it to turn. The registering needle is on the cen- 
ter staff. The hair spring serves to dampen vibration and 
assist in the return movement. See plate 12. 



212 



PLATE 12 



SCREW HOLE FOR MQWTIN(t 
CASE FLANG-E 
UPPER PLATE 



CENTER. STAFF, PINION 
* HAIF^SPRINCi- \o 



BOOgPEN TUBE 



MAIN PLATE 




CONNECTING LINK 

_ SEG-MENT 



CASE FLANG-E 



PRESSURE GAU&E 



CHAPTER XXX 
The Side Slip Indicator 

The side-slip indicator is valuable as a means for checking 
the accuracy of the pilot's judgment in flying, and is par- 
ticularly useful in the larger types of aircraft where the pilot's 
cabin is inclosed. 

In an open machine the pilot can tell by the wind pressure 
on his cheek when he is making a faulty turn. Increased 
pressure on the right cheek on a right hand turn indicating 
an inward side-slip to the right, increased pressure on the left 
cheek under similar conditions would indicate an outward 
side-slip, or skid to the left. 

The instrument is of very simple construction consisting 
of a curved glass tube filled with a mixture of alcohol and dis- 
tilled water to prevent freezing, and usually colored to aid 
visibility. The glass tube is mounted in a suitable holder 
as shown in plate 13, the holder being marked with an 
angular scale. 

When the machine is flying level the bubble is in the center 
which is marked zero degrees. When a wing is lowered the 
bubble moves away from the low side, but in a properly made 
turn the resultant of the combined forces, gravity and centrif- 
ugal, is a line drawn directly through the center of the air- 
craft and the bubble will remain at zero degrees as the cen- 
trifugal force which tends to throw the liquid outward will 
have been neutralized by a proportional addition of gravity 
in banking the plane. 

Practically no repairs can be made to this instrument, a 
broken tube necessitating a replacement. 

213 



214 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



Great care should be exercised when installing the instru- 
ment to have the aircraft level laterally and that the bubble 
be exactly in the center over zero degrees when the indicator 
is attached to the instrument board. 





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CHAPTER XXXI 

The Fore and Aft Level 

The fore and aft level as shown in plate 14 consists 
simply of a triangular glass tube having a bulb in the apex 
of the triangle. 

The tube is partially filled with a non-freezing colored 
liquid. The level is set flush with the instrument board and 
graduated in degrees, the zero degrees being in the half way 
position when the plane is flying level fore and aft. This 
level shows the pilot the degree of climbing or gliding angles 
of the plane under a given set of power or load conditions. 

Unlike the air speed meter, which as we know shows the 
pilot at all times whether he is flying within a safe margin of 
speed, the fore and aft level cannot be used to check the climb 
as a plane might climb at a certain angle with a full "gun" 
and a light load while with a full load and a failing engine the 
angle of climb would be less. 

The greatest value of the instrument lies in its use on bomb- 
ing and photographic planes where it is imperative that the 
craft be kept on a level keel. 

Care must be used when installing to have the bubble at 
zero degrees when the plane is exactly level fore and aft. 

No repairs or adjustments can be made on this instrument. 



215 



CHAPTER XXXII 

The Gyro Turn Indicator 

The primary purpose of the gyro turn indicator is to make 
fog, cloud and night flying easier and safer. " It does this by 
showing, instantly and accurately, the least divergence from 
straight line flight. 

Its mechanism is extremely simple. A small gyro, on a 
lateral axis, is spun to about 5000 revolutions per minute by 
the suction obtained from a venturi tube placed in the air 
stream and connected to the instrument by a length of tub- 
ing. The frame holding the gyro bearings, is hung on a fore 
and aft axis, but its rotation about this axis is restrained by 
light centralizing springs. 

The action of the instrument depends upon the well known 
law of gyroscopic precession — that is, any rotary motion 
transmitted to a gyro (except motion about its own axis) 
eauses the gyro to move, not in the direction of the applied 
motion, but at right angles to it. This motion at right angles 
to the applied motion is called "precession." Furthermore, 
the speed at which a gyro will "precess" is many times greater 
than the speed at which the rotary motion is applied to it. 

The operation of the indicator is thus very simple. When 
the airplane starts to turn (about a vertical axis) the rotary 
motion causes the gyro to precess (about a horizontal axis) 
and this precession, many times greater than the turning 
motion of the airplane, is indicated on the dial of the instru- 
ment. Were it not for the centralizing springs, the slightest 
turning motion of the airplane would cause the gyro to pre- 
cess all the way round. The springs are used, therefore, to 
restrain the action and so that fast or slow turns produce 

216 



THE GYRO TURN INDICATOR 217 

large or small indications. As soon as the turning motion 
ceases, the springs return the gyro to the neutral position. 

Any one who has had the disconcerting experience of find- 
ing himself in fog or cloud, with no means of knowing when 
he was turning, will appreciate what a tremendous advance 
in the art of aerial navigation is made possible by this little 
instrument. 

The Gyro Turn Indicator, complete with a venturi tube 
for operation, weighs but If pounds. The power required 
to operate the instrument is no more than that needed for an 
air speed indicator. 



CHAPTER XXXIII 
Hydkogen Leak Detectok 

The hydrogen leak detector shown on the following page 
is mounted for use in a circular wood frame about 10 inches 
in diameter. The dial can be read on the front of the frame, 
while the back of the frame is covered with a perforated metal 
plate and a disc of wire gauze to protect the clay disc of the 
instrument from injury. 

To operate, the frame is laid against the gas bag with the 
perforated plate inward and the dial facing the operator. 
Hydrogen leaking from the gas bag anywhere in the area 
covered by the frame passes through the perforated plate 
and wire gauze and comes in contact with the clay disc. 
This disc is impervious to air, but permits the passage of 
hydrogen, which, when it passes through into the air tight 
compartment increases the pressure in this compartment 
and forces the flexible metal diaphragm out slightly. This 
movement is transmitted through the lever roller, lever, and 
shaft and slacks the operating thread against the pull of the 
helical spring. The hair spring takes up this slack through 
the pinion, and gear sector, causing the index hand to move 
on the dial. 

After the test, and when the hydrogen in the air tight com- 
partment has been allowed to escape through the clay disc, 
the diaphragm returns to its normal position, and the helical 
spring, which is more powerful than the hair spring, pulls the 
thread back to its original position and causes the index hand 
to return to the zero mark on the dial. 

In order to compensate for temperature and barometric 
pressure variations, and in order that the index hand will 

218 



PLATE 14 




HYDROGEN LEAK DETECTOR 219 

point to zero on the dial when there is no hydrogen in the 
air tight compartment, an adjusting thread and clamp is 
provided. See plate 14. 



CHAPTER XXXIV 

The Manometer 

The U-tube manometer is an instrument used to register 
the gas pressure in balloons and ariships and air pressure in 
ballonets. 

The instrument is composed of three tubes, two of which 
are metal, and one of glass, which gives the readings. The 
two metal tubes are placed one on each side of the center 
glass tube and are connected to each other at both ends by 
small reservoirs. The glass tube is only connected to the 
lower reservoir and has a very small air hole in the top end. 
The lower reservoir is filled with a kerosene mixture. 

When the pressure is placed on the instrument, it travels 
down the two metal tubes to the lower reservoir where it 
forces the liquid into the glass tube. As the liquid travels 
up the glass tube, it forces the air out through the small hole 
at the top. As the pressure drops, the action is reversed. 
See plate 15. 



220 



PLATE 15 



AIR VENT 




CHAPTER XXXV 

The Statoscope 

Strictly speaking, statoscopes are used mainly on airships 
and free balloons but are sometimes used on airplanes in 
tests. 

There are two types of statoscopes, namely : the liquid and 
diaphragm. The liquid type is the simpler of the two as 
there is no mechanism to get out of order. The various dia- 
phragm types are similar in design and construction but are 
rapidly falling into disuse, owing to the rapid deterioration 
of the rubber diaphragm. 

THE LIQUID TYPE 

It consists of a curved glass tube which is enlarged at both 
ends, one end leading to an enclosed reservoir and the other 
end is open to the atmosphere. A small drop of oil (about 
\ inch long) is dropped into the tube, thus sealing the air in 
reservoir. 

When ascending, atmospheric pressure grows less, so the 
pressure in the reservoir becomes greater than the pressure 
outside and as a result the liquid is forced towards the outlet 
end in order to equalize the pressure. The instrument is 
extremely sensitive and in order to prevent the bubble from 
getting to the end of the tube too quickly, the ends are en- 
larged. On reaching the enlarged end, the bubble will break 
run down toward the bottom part of the tube and form over 
again. If the instrument is still going up, the procedure will 
be repeated. A trap is placed in each end of the tube so that 
the instrument may be carried in any position without losing 

221 



222 



the oil. The entire instrument is wrapped with an insulating 
composition, such as cotton, felt, or similar substance, to 
protect it from sudden temperature changes. This substance 
must not be removed when the instrument is in operation. 

The black marks on the narrow portion of the tube are 
placed there in order to aid in the reading of slight changes. 
A well made instrument will register changes of elevation as 
small as one inch while changes of 10 feet or more will register 
on the crudest of instruments. 

The liquid is a kerosene mixture to prevent freezing. See 
plate 16. 



PLATE 16 




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CHAPTER XXXVI 

Balloons 

The first balloon said to have been flown for public exhibi- 
tion was on June 5, 1783, by Joseph and Steven Montgolfer. 
The first man to go up in a balloon was said to have been a 
man by the name of Rozier, who ascended in a captive balloon 
to a height of about 80 feet, in the latter part of the year 1783. 
Later, in company with a companion, he made a voyage in a 
free balloon, remaining in the air about half an hour. These 
balloons were inflated by hot air and by means of a fire pan 
carried immediately below the mouth of the bag the air was 
kept at sufficient temperature in order to keep them in the air. 

The first really successful free balloon crossed the English 
Channel in 1785. An Englishman by the name of Blan- 
chard and an American by the name of Jeffries started from 
Dover on January 7 in a balloon equipped with wings and 
oars. After a very hazardous voyage, during which they 
had to cast overboard everything movable to keep from 
drowning, they landed in triumph on the French Coast. An 
attempt to duplicate this feat was made shortly afterward 
by Rozier. He constructed a balloon filled with hydrogen, 
below which hung a receiver in which air could be heated. 
He hoped to replace by the hot air the losses due to leakage 
of hydrogen. Soon after the start the balloon exploded, due 
to the escaping gas reaching the fire, and Rozier and his 
companion were dashed on the cliffs and killed. 

The fact that the invention of the airship and means 
of navigating it were almost simultaneous with the free 
balloon and the principles upon which success has been 
achieved were laid down within a year of the appearance of 

223 



224 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Montgolfer's first gas bag. The development was very 
much retarded by the lack of suitable means of propulsion 
and the actual history of what has been accomplished in this 
field dates back only to the initial circular flight of La France 
in 1885. Lieutenant Meusnier, who subsequently became a 
General in the French Army must really be credited with 
being the true inventor of aerial navigation. At a time 
when nothing whatever was known of the science, Meusnier 
had the distinction of elaborating at one stroke all the laws 
governing the stability of an airship and calculating correctly 
the condition of equilibrium for an elongated balloon after 
having strikingly demonstrated the necessity for its elonga- 
tion. This was in 1784 and Meusnier 's designs and calcula- 
tions are said to be still preserved in the engineering section 
of the French War Office in the form of drawings and tables. 

But as often proved to be the case in other fields of re- 
search, his efforts went unheeded. How marvellous the 
establishment of these numerous principles by one man in a 
short time really is, can be appreciated only by noting the 
painfully slow process that has been necessary to again de- 
termine them, one by one, at considerable intervals and after 
numerous failures. Through not following the lines which 
he laid down, aerial navigation lost a century in futile grop- 
ing about; in experiments absolutely without method or 
sequence. 

It is to be noted that during the period between 1784 and 
1885 the development of the airship was very much re- 
tarded by the lack of suitable means of propulsion. There- 
fore, all of the laws governing the stability of an airship and 
calculating correctly the equilibrium for an elongated balloon 
were not put into practice until the latter date mentioned. 

Q. How many kinds of gases are there used for bal- 
looning? 



BALLOONS 225 

A. Three— rrydrogen, helium and coal gas. 

Q. Which has the greatest lift? 
A. The lift of the foregoing gases is as follows: 
Hydrogen, helium, coal gas. 

Q. Which is the best gas of the three? 

A. Helium is the best of all known gases for ballooning 
owing to it being non-poisonous and non-explosive, but its 
use is limited at the present time, owing to limited quantity 
available and its excessive cost. Hydrogen is the best of 
the three if cost and buoyancy are taken into consideration, 
but it is highly dangerous when impure, and is subject to 
ignition through both spontaneous combustion, static elec- 
tricity, fire, etc. Coal gas is only used for free balloons and 
those carrying a large volume of same as its lift is only about 
one-half that of hydrogen, its cost being less than one-tenth 
of that of hydrogen. 

Q. How many processes are there for making hydrogen 
gas, and which is the cheapest? 

A. There are various methods for making hydrogen gas. 
Some of them are as follows: 

1. The Electrolytic Method, which is the process of separat- 
ing the hydrogen from the water by means of an electric 
current. By this method 1 kilowatt hour of electric power 
will produce about 1\ cubic feet of hydrogen at a cost of 
about S8.00 per 1000 cubic feet. 

2. The Silicon Process: The chemical reaction producing 
hydrogen is between silicon and caustic soda without any 
change in the iron. Ferro-silicon is used by the French and 
British, being more easily secured and at less cost than the 
pure silicon. Ferro-silicon contains from 50 to 75 per cent 
silicon. It is believed that to produce 1000 cubic feet of 
hydrogen by this method 39.6 pounds of pure silicon and 



226 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

112.3 pounds of pure caustic soda will be required. The 
actual quantity produced depends upon the purity of silicon 
and caustic soda. The ferro-silicon has been found to pro- 
duce as high as 85 per cent silicon. 

3. Steam and Iron Process: Hydrogen is made by passing 
steam over the red hot iron ore. The steam is decomposed 
into its constituent elements, the iron ore absorbing oxygen 
from the steam and the hydrogen being collected. It is 
believed that 3500 cubic feet of gas per hour can be manu- 
factured by this process, at a cost of from $5.00 to $7.00 per 
1000 cubic feet. This process is the one now used at Pensa- 
cola, and it is believed that the cost can be considerably re- 
duced by running the plant continuously, which is not done 
at present. 

4. Another process is the vitriol process, which is the ac- 
tion of sulphuric acid on iron or zinc, evolving hydrogen. It 
seems that 150 pounds of iron and 275 pounds of sulphuric 
acid are required to produce 1000 cubic feet of hydrogen, and 
182.5 pounds of zinc and 275 pounds of sulphuric acid are 
required for 1000 cubic feet of hydrogen. 

5. The Hydrolythe Process: To produce hydrogen by this 
method it is only necessary to drop the granulated hydrolythe 
into the water. Not extensively used due to high cost of 
hydrolythe. To produce 1000 cubic feet of hydrogen only 
59 pounds of hydrolythe are required. There are several 
other methods, but the steam and iron process seems to be 
the cheapest and used most extensively at present. 

The above mentioned gases are the principal gases used 
for ballooning. Natural gas can be used as well as those 
previously described. It consists of about 90 percent marsh 
gas and 10 per cent of other hydro-carbons. It is a very ex- 
plosive gas, being similar in composition to the fire damp 
found in coal mines. It is a cheap gas, but has very little 
lifting power. Its lift is about equal to that of air heated 



BALLOONS 227 

from 60°F. to 150°F. Its specific gravity averages about 0.66. 

Water gas is so called because it is made from water or 
steam. It constitutes the basis of the illuminating gas used 
in most cities at the present time. Super-heated steam is 
passed through red hot carbon, either in the form of coke or 
hard coal, giving the following reaction: H 2 + C = CO + 
2H. This combination of CO and H being water gas. 

Hot air gas has been used to a certain extent for exhibition 
free ballooning, but it is not suitable for airships or free ball- 
oons, and it is not considered safe to descend with a hot air 
balloon, hence the descent is always made by a parachute 
where hot air is used. 

The question as to the cost of producing hydrogen varies 
considerably in that the cost of materials varies more or less 
and the length of time the plant is operated, particularly the 
iron contact process, which plant, in order to obtain the best 
results, should be operated day and night, and while hydro- 
gen can be manufactured cheaply by this method it will be 
found, when the cost of renewal of equipment is taken into 
consideration, such as the periodical renewal of retorts, that 
the cost of producing hydrogen by this method is liable to 
be misleading. It is to be noted that by the electrolytic 
method hydrogen can be manufactured for from $8.00 to 
810.00 per 1000 cubic feet. Under the silicon process, ac- 
cording to the chemical action to produce 1000 cubic feet of 
hydrogen would require 39.6 pounds of pure silicon and 112.3 
pounds of pure caustic soda. The actual quantities which 
should be supplied depend upon the silicon content of the 
ferro-silicon and the percentage of purity of the caustic soda. 
It has been ascertained that 58 pounds of 80 percent ferro- 
silicon and 125 J pounds of caustic soda would produce 1000 
cubic feet of hydrogen. Ferro-silicon at 15 cents per pound 
and caustic soda at 3 cents per pound would bring the total 
cost for material to $12.46 per 1000 cubic feet. In connec- 



228 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

tion with the manufacture of hydrogen by the silicon proc- 
ess, it is to be noted that f erro-silicon may be stored without 
deterioration by moisture and without any special precau- 
tions for its care. However, such is not the case with caustic 
soda, which must be protected from moisture. 

Q. What should be the percentage of purity of this gas 
as manufactured? 

A. The percentage of purity of hydrogen gas as manu- 
factured at Pensacola averages 99.8 per cent pure (steam and 
iron process), the electrolytic process 99.9 and the silicon 
process 99.8. 

Q. What is diffusion? 

A. By diffusion (with reference to ballooning) is meant 
the volume of gas which passes through a unit area of balloon 
fabric in a given time under certain or standard condition. 
These requirements vary greatly with the purpose for which 
the fabric is to be used, as for instance a free balloon need not 
be so tight as an airship. 

PERMEABILITY TEST 

The permeability of the fabric to hydrogen shall be 
determined from a representative specimen of the fabric 
selected from the test sample under the following condi- 
tions and by an approved method and apparatus. The 
fabric shall be maintained during the period of test at a tem- 
perature of 25° C, and a current of pure, dry hydrogen shall 
be maintained on one side of the fabric during the period of 
test under a pressure of 30 mm. of water above the pressure 
on the reverse side of the the fabric. Dry air at approx- 
imately atmospheric pressure shall be passed over the 
reverse side of the fabric, and the hydrogen passing through 



BALLOONS 229 

the fabric shall be determined either by burning to water 
and weighing as such or by any other accurate method, such 
as using the gas interferometer. If the combustion method 
is used, the fabric should remain in the apparatus in con- 
tact with the atmosphere of pure hydrogen for a sufficient 
period to reach equilibrum before beginning a test. The 
permeability shall be calculated in liters of dry hydrogen, 
measured at zero degrees centigrade and 760 mm. mercury 
pressure, and shall be expressed as the permeability in liters 
per square meter per 24 hours which shall not exceed the 
maximum called for. 

Q. How is the purity of the gas tested in a balloon or 
airship and how often? 

A . The hydrogen gas contained in an airship is tested by 
two methods: First, the pyrogallic acid absorption outfit; 
Second, the Edwards effusion meter. 

In testing with the absorption outfit, the manometer tube 
is taken from the manometer and placed on the inlet tube of 
the absorption outfit. One hundred cubic centimeters of 
hydrogen are taken into a pippette graduated in tenths of 
cubic centimeters in the absorption outfit. After this gas 
has been taken in, it is forced through a pippette containing 
broken glass tubing saturated with pyrogallic acid. The 
pyrogallic acid robs the balloon gas of the oxygen contents. 
After washing two or three times the gas is brought back, 
and measured in the tube graduated in tenths of cubic centi- 
meters and subtracted from the original amount, which was 
one hundred cubic centimeters. The difference in the two 
volumes is the oxygen content of the gas, which has been 
absorbed by the pyrogallic acid. As oxygen is approxi- 
mately one-fifth of the air content, this result is multiplied 
by 5 which gives the total impurity of the balloon gas; total 
impurity being air. 



230 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

EDWARDS EFFUSION METER 

The construction of the meter includes a glass jar in a 
water jacket with two hair lines on it. It also includes an 
orifice and a levelling bottle which is filled with water. In 
testing hydrogen gas with this type of meter, the manometer 
tube is disconnected from the manometer and connected to 
the meter same as for other outfit, and gas from the airship 
is allowed to pass into the meter through a stop cock, which 
is shut off immediately after the entrance of the amount re- 
quired for the test. The gas is then forced through the orifice 
by means of the levelling bottle filled with water. From the 
time that the water level forcing the gas through the orifice 
reaches the first hair line in the jar until the time that the 
water level reaches the second hair line, this passage is timed 
with a stop watch in fifths of a second. This operation is 
carried out three times and the average taken. Then air is 
taken and a similar procedure followed, repeating three 
times. The gas time is divided by the air time and a factor 
or number thereby obtained. From this factor the specific 
gravity of the balloon gas is determined by referring to a 
chart or conversion table, and from the specific gravity the 
purity of the balloon gas is determined. 

Q. What is meant by purging a balloon? 

A. Purging is the substitution of pure gas for a quantity 
of impure gas contained in an airship. To purge a balloon 
either one or both of the ballonets may be used. The amount 
of gas necessary to bring the purity up to a safer margin may 
be from 20,000 to 30,000 cubic feet. The ballonets in an 
airship being about 25 to 30 per cent capacity of that of the 
gas bag can be filled with air, valving the gas from the bag 
proper as ballonets become full. The gas valve is then 
closed and new and purer gas is started into the gas bag. 



BALLOONS 231 

The valves of the ballonets being opened the air is forced out 
until the diaphragms of the ballonets lie flat on the bottom 
of the balloon and the gas pressure shown by the manometer 
is } inch or 1 inch as may be desired. 

Q. If, on testing, a balloon shows 18 per cent volume of 
air, what percentage of oxygen would it contain? 
A. About 3.6 per cent of oxygen. 

Q. What percentage of air is oxygen by volume? 
A. Approximately one-fifth. 

Q. What is a com along and for what purpose is it used? 

A . A comalong is a cable grip, used for hauling taut sus- 
pension wires on airships or it can be used on wire where 
slack in same is desired to be taken up. As a rule coma- 
longs or cable grips only have a range for about three 
different diameter wires. Therefore, a comalong for use 
on J inch or T \ inch diameter cable would not be suit- 
able for \ inch diameter cable, this being governed by the size 
of the jaws and the depth of groove in same. The comalong 
is operated by pulling the lower jaw towards you and pushing 
the upper jaw away from you, thus opening the jaws. Place 
wire between the opening between the upper and lower jaws 
and let go the jaws. It will automatically grip the wire on 
account of a spring arrangement which causes jaws to close. 
A small jigger or tackle is then attached to the eye and cable 
is hauled taut. 

See figure on following page. 



232 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



Cable: Gctztr otz Gome 



•ALONGi 



INGI- 




/5HA 



CKLE 



<5:RIPPIN€r F^dlTION ON CABLE 



SHACKLE 




Open Rssition to Receive Cable. 
Fig. 22 



CHAPTER XXXVII 
Transportation of Gas 

Q. How many means are there for transporting gas? 

A . Three — by the means of nurse balloons, steel bottles 
and gas pipe lines. 

Nurse. Gas is often transported from one place to another 
by the use of the "nurse" when the distance is not too great. 
The "nurse" is nothing more than a fabric container holding 
probably 5000 cubic feet of gas. This bag is usually made 
cylindrical with hemispherical ends and equipped with ropes 
on either side for the purpose of transporting it from one 
place to another. 

Bags of sand are attached to these ropes so that the weight 
of the sand almost equals the lift of the gas. In this way, 
the only force to overcome is that due to the wind. 

In crossing wires, the first pair of ropes are thrown over 
the wires and caught again on the other side, then the second 
pair, etc., until the gas bag has been literally carried over the 
wires. The gas can be taken from the "nurse" in two ways, 
either by the application of pressure on the bag, or by having 
the outlet in the top of the bag and depending upon the light- 
ness of the gas to leave the bag, or both. 

Bottle. The most usual method of transporting gas is by 
the use of gas bottles. These bottles vary in size, the most 
usual size having a total height of about 4. feet 3 inches and an 
outside diameter of approximately 8| inches. These bottles 
are pressed from steel and have no seams. The wall of 
these bottles is from \ to \ of an inch thick. When charged 
to a pressure of 1800 pounds, which is the usual pressure to 

233 



234 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

which these bottles are filled, they contain a quantity of gas 
which when released to atmospheric pressure has a volume 
of from 175 to 200 cubic feet. 

A specially constructed needle valve is required to prevent 
the escape of gas at this high pressure. 

When emptying these bottles a great decrease in the tem- 
perature takes place at the valve due to the sudden adiabatic 
expansion of the gas, causing frost, and even freezing the out- 
let completely shut, cutting off the supply of gas and giving 
the impression of an empty bottle. The valve must be 
thawed out before the remainder of the gas can be obtained. 
This freezing can be eliminated and the entire quantity of 
gas discharged quicker by opening the valve only part way, 
hence keeping the gas temperature from dropping to such a 
low degree. After the pressure in the bottle has decreased 
somewhat, the valve may be opened wider. 

For military purposes, trucks are arranged with shelves so 
that several layers of bottles can be transported at the same 
time ; the bottles are all clamped in place so that they cannot 
jar about. In order to facilitate rapid gas bag inflation, all 
of the bottles of each row are connected to one main and 
the several mains connected together, so that all that is neces- 
sary to discharge the contents of perhaps two dozen bottles 
is to attach the inflation tube to this manifold and turn all 
the valves slightly. 

For storage and transportation afloat bottles would be 
used. 



CHAPTER XXXVIII 
Interior Inspection of Balloons and Airship 

Q. What inspection is necessary before inflating a free 
balloon, kite balloon and airship with hydrogen? 

^4. Before inflating a free, kite balloon, or airship with 
gas : The bag should first be spread out on the ground cloth 
and inflated with air to about one-quarter full, for the pur- 
pose of inspecting the fabric, seams and rip panels, and all 
valve openings, also glands and appendix connections inside 
and out. Depending on the size of the bag, the inspection 
crew may consist of four, six or ten men and in larger types 
of airships larger crews. The fabric is inspected for scratches 
and pin holes; deep scratches often occur where the bag comes 
in contact with the floor. Places may be worn where ropes 
rub on the bag during inflation. Seams and the tape cover- 
ing them are examined to see that all are sound and in per- 
fect condition. An examination of the fabric and stitching 
and cementing of all finger patches, fins and rudder connec- 
tions, ballonet diaphragm, and in the case of kite balloon 
the belly band and lobe connections. In this connection it 
is noted that one crew works on the outside of the bag while 
another is inside, the work being done systematically, each 
block of fabric being gone over carefully. In order that the 
minutest hole can be detected a man on the outside of the 
bag has a rectangular shaped box with three or four electric 
lights therein, which he holds up against the fabric and passes 
over a section at a time, in order that the man on the interior 
of the bag can readily detect same. By this means any hole, 
no matter how small, is easily detected from within, this 
however is only used on airship inspection. 

235 



236 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Note: Before entering any balloon or airship for inspection 
purposes or otherwise, make sure that the bag has been fully de- 
flated and that no hydrogen remains before partially inflating the 
bag. 



Q. If, upon inspection, any holes or thin places are lo- 
cated, state in detail how same may be remedied. 

A. If any holes are found, cut a patch to cover and wash 
both surfaces with benzine. Apply three coats of pure 
rubber cement both to the balloon and the patch, allowing 
sufficient time for the first and second coats to dry and 
enough time for the third to become tacky, then apply the 
patch and roll hard, care being taken to get all air pockets out 
and the edges tight, then apply soapstone to prevent stick- 
ing. For small holes a fabric patch on the inside only is 
necessary, larger ones inside and out, scalloping the edges of 
the patch, and making the inner patch slightly larger. Holes 
requiring a patch with a side more than twelve inches are usu- 
ally done by an experienced man, and the .rule is that the 
edge of the patch should in no case be nearer than three inches 
from the edge of the hole. When large areas of thin fabric are 
found, they are usually repaired by removal of the panel, or 
block as sometimes called, and this work must be done by ex- 
perienced and efficient men after the bag has been deflated, 
the tape inside and out being removed and the panel care- 
fully cut out, a new panel cut to fit the edges, having a lap 
of about one inch. The edges of the new panel for li inches 
are cleaned with high test benzine, also the edges of the open- 
ing in the bag, and three coats of pure rubber cement applied 
with fifteen minutes between each coat. As soon as the 
last coat becomes tacky • the patch is applied and care 
taken to get all wrinkles and air pockets out by running a 
small steel roller well over the seams. The seams are then 
double stitched and then prepared with two coats of cement 






INTERIOR INSPECTION BALLOONS AND AIRSHIPS 237 

and tape applied and rolled down well, especially on the edges 
of the panel fitted. The patch is then coated with the air- 
ship dope (Delta Dope) inside and out. 

Q. In valving a balloon to relieve gas pressure does or 
does not a certain amount of air enter the balloon at the same 
time? If so, what percentage of volume in proportion to the 
amount let out? 

A . It is believed that a certain small amount of air does 
enter a balloon when it is being valved to relieve gas pressure, 
about 0.4 per cent of volume in proportion to the gas let out. 

Q. What is a rip panel and for what purpose is it used? 

A. A rip panel is a part or section of a balloon so con- 
structed that it can be opened at a monent's notice to allow 
the gas to escape more rapidly than the valves would allow 
and is so located as to be at the top of the bag in a spherical 
balloon or any other type. The opening, when panel is 
ripped, if old type, is about 4 inches wide and varies in length 
from 6 to 18 feet, depending on the size of the bag. And if 
the new type*, the rip panel consists of a series of openings 
about 8 inches by 12 inches, elliptical in shape, and about 
8 to 12 inches apart, and in a straight line so that a narrow 
strip of fabric will cover all of these openings, used in kite 
balloons only. A panel of this type is considered stronger, 
and there is less danger of the balloon being ripped by the 
wind beyond the point intended, as might be the case with the 
first type mentioned. The panel proper is a strip of fabric 
wide enough to allow for cementing and sewing it to the bal- 
loon at edges only and for a length sufficient to allow for 
turning the upper end back over a toggle to which the rip 
cord is attached. The cementing at this end of the panel is 
brought to a sharp point after clearing the margin of the last 
opening. This is to make the rip start easily and without 



238 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

tearing the fabric. The principal use of the rip panel is to 
deflate the balloon rapidly in the case of an emergency when 
it is not safe to undertake to make a landing by valving. 

Q. State in detail how you would put a rip panel on a free 
balloon, airship or kite balloon. 

A. In a free balloon the rip panel is located in the upper 
hemisphere, the top of the panel being about 4 feet from 
the valve hole, and running in the direction of a meridian. 
The length of the panel, if of the slot type, is usually one- 
sixth the circumference of the bag, or from 12 to 24 feet in 
length and 4 inches wide, depending upon the size of the bag. 
This type of rip panel is installed in the following manner: 
The section where panel is to be cut is reinforced with two 
thicknesses of balloon fabric cemented to balloon, one inside 
and one outside, the inner being about 10 to 12 inches wide 
and the outer 9 to 11 inches, and about one foot to 14 
inches longer than the slot is to be. The slot is then cut 
through the bag and reinforced and the edges of the slot 
taped with a 2-inch tape which leaves nearly one inch 
inside and one outside, a double row of stitchings then 
runs around the slot through fabric and tape. This 
will prevent the tape from becoming loose and keep the 
edges of the slot in good condition for replacing the rip 
panel from time to time. The panel itself which is cemented 
on to the balloon over the slot on the inside is made of 
two to four thicknesses of balloon fabric cemented together. 
The edge is taped, the ripping end of the panel is folded back 
over a toggle, and this fold back is cemented down to the 
panel itself. The panel is cemented to the balloon. Beyond 
the ripping end of the panel there is cemented to the balloon 
an anchor patch. The ripping end of the panel is tied to this 
patch by two breakable cords which are of different lengths 
so that one breaks before the other. There is also another 



INTERIOR INSPECTION BALLOONS AND AIRSHIPS 239 

small patch with breakable cords to take the weight of the 
rip cord. A pull of 30 pounds is required to break these 
cords before the panel will start to rip. This is an extra pre- 
caution. Additional patches with breakable cords may be 
placed to suit the lead of the rip cord down to the car, in 
some cases tape being used on the outside. One other type 
of rip panel used at present is that of a series of elliptical 
holes. 8, 12 and 16 holes being cut through the reinforced 
fabric, the edges taped, and in some cases rope grommets are 
used on these edges for reinforcements. The holes are spaced 
4 to 6 inches apart and the rip panel is cemented on to the 
balloon from the inside, edges and ends only, no cementing 
to the space between each opening. The panel itself is of 
two thicknesses of fabric with the edges taped, and the rip- 
ping end same as that mentioned above. There seems to be 
a great advantage in the strength of this type of rip panel 
over the slot type, but it is believed that the slot type is the 
most efficient type when it becomes necessary to make use of 
the rip panel of a balloon. In a number of ships built 
for the Navy three and even four rip panels have been fitted, 
two on the bow and two near the tail or on the quarter on 
either side of the ship. This is an advantage for when rip- 
ping the panel in the bow of a ship which is headed into a 
strong wind the wind will tend to keep the gas in the bag, and 
by ripping one or both of the rear panels the gas will be driven 
out by the wind much more rapidly. This also would apply 
when ship was broadside to the wind. The panels on the 
opposite side could be ripped in order to deflate and save the 
ship. Also another type has rip panels from which the 
rip cords lead so that they can be ripped singly or 
collectively. This permits the rip cords to be tied to a 
mooring post when the ship is anchored. The R and M 
type kite balloons are fitted with one rip panel forward 
near the nose at the greatest diameter of the bag; in the 



240 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

R type the rip panel is transverse and of the elliptical 
hole type. In the C type ship two panels are fitted in the 
top. Rip cords are always colored red. 

Q. What is delta dope and for what purpose is it used? 

A. Delta dope conforms to airship dope specifications 
No. 44 and the solvent and thinner to specification No. 45. 
It is used to dope the inside and outside of airships and bal- 
loons, and its principal function is to make the bag gas tight. 
When carefully and evenly put on, it has a smooth finish 
film and offers a greater resistance to gas leakage than 
plain dope, and on account of the castor oil in it reduces 
somewhat the tendency to crack the surface. 

Q. For what purpose is powdered aluminum used on a 
balloon? 

A . Powdered aluminum is used on balloons for radiation 
purposes. The outside surface of the bodj^ painted with dope 
or varnish containing aluminum of 5 to 8 per cent (by 
weight) to the gallon reflects the heat from the sun more 
effectively than any other material used in painting balloons 
or airplane wings, thus keeping the temperature inside the 
balloon as low as possible. 

Q. What percentage of powdered aluminum by weight 
should be put in each gallon of dope? 

A . From 5 to 8 per cent by weight powdered aluminum 
should be put in each gallon of dope for the outside of a 
balloon. 

Q. How many square feet of surface will delta dope cover 
per gallon? 

A. In the first coat work 125 square feet r^gr gallon; in 
each additional coat 150 square feet per gallon, dope con- 
taining aluminum about 125 square feet per gallon. 



INTERIOR INSPECTION BALLOONS AND AIRSHIPS 241 



Q. What methods are used in applying this dope and de- 
scribe same? 

A. There are two methods, the spray guns and brushes. 
The former method always gives the best results. The bag 
is inflated with air and kept well ventilated for the inside 
doping, the crews being changed quite often in order that no 
one may be overcome by the fumes. The bag is rolled from 
side to side on the ground cloth as the dope is applied, the 
gangs taking the width of one or two gores at a stretch until 
the entire bag has been coated. The gore is the panel run- 
ning lengthwise with an airship or kite balloon, and the per- 
pendicular panels in a free balloon are the gores. The rings 
are the transverse or horizontal panels. The usual precau- 
tions of seeing that the bag has been fully deflated and that 
no hydrogen remains when the bag is inflated with air in order 
to work in same should be observed. 

Q. What is a gammeter valve and for what purpose is it 
used? 

A. Gammeter is the name of the person who designed 
the balloon valve of that name. It is used in kite balloons 
and airships both for air and gas valves, works by hand and 
automatically when adjusted for certain pressure. Is used 
to relieve gas or air pressure in the envelope and ballonets. 
The gammeter valve is an all metal valve, while free 
balloons are fitted with a wooden valve operated by hand 
only. 

Q. Describe a gammeter valve. 

A. The gammeter valve is composed of the following 
parts: An aluminum ring with three bars connecting to a 
center post, or barrel; in this barrel is fitted a sliding bolt or 
pin, to which three arms connected by pin connection at top 






242 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

of sliding bolt and at lower end by a short rocker arm to the 
fixed arm of the frame. Also three spiral springs, one for 
each arm, connect to the lug on each arm and to an adjust- 
able nut at the upper end of the barrel. There is also an 
adjusting mechanism for setting the valve to open auto- 
matically at a certain pressure from within. There is 
another clamping ring with wing nuts for clamping the en- 
velope fabric between ring and valve frame. A cover of 
aluminum which is attached to the lower end of the sliding 
bolt, is slightly belled at edges and fitted with a flange 
which forms a suitable seat for the rubber gasket which 
is held in place by metal clips or by a wrapping of harness 
twine. The outside surface of the cover is practically flat 
except as noted above and has an eye in the center to which 
the valve cord is attached. On the inside of the valve cover 
there is a thin sheet of aluminum riveted at edges which 
rises cone shape to the bottom of the fixed arms of the valve 
frame. A guard made of aluminum sheet lightened with 
several 2 inch holes, cone shaped, is fitted on the inside of 
the valve ring. This guard protects the post adjusting 
and operating gear of the valve from all except dust, sand 
or other small particles that may be in the air. The mould- 
ed rubber gasket fitted as above mentioned to the cover 
seats on the smooth flat surface of the main ring of the valve 
frame, and if kept clean and in good condition makes a very 
gas-tight joint. The gammeter valves used in kite balloons 
and airships are 12 and 18 inches in diameter. The valve 
can be adjusted before or after installation in the envelope 
as the adjusting screw is located on the outer surface of the 
valve. There is also fitted on the outside of the valve a 
yoke with a tripping lever and spring. (See Fig. 23.) 

Q. What is the valve seat composed of? 

A. The valve seat is composed of a moulded rubber 




Fig. 23 
243 



244 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

gasket with the flange about f inch wide, and secured to 
the cover by metal clips or by a wrapping of harness twine, 
also cemented to the flange of the cover. 

Q. How is a balloon of any kind inflated from flasks? 

A. In inflating a balloon from flasks, compressed gas 
is used. Cylinders containing about 180 cubic feet each of 
hydrogen gas are placed at the end of the hangar, that is 
if the balloon is in a hangar. The flasks are placed in stacks 
with the valve ends toward each other, with a passage 
between them just wide enough to allow for attaching the 
manifold connections to the cylinders. The cylinders 
are usually placed in groups of 100, 200 or 300, depending 
upon the capacity of the balloon to be filled. The cylinders 
are so arranged that connections to manifolds can be easily 
made without having to move anyone of the flasks. This 
is done by slightly staggering the successive rows of flasks 
toward the rear giving sufficient clearance for removing the 
screwed cap, making the connections and operating the 
valves. The manifold is usually of 6 branches, but may be 
of more, made of cast brass or bronze. The inside diameter 
is about f inch, and the dead end of the manifold should be 
solid, not a mechanical or welded joint. The fabric inflation 
tube is connected to the manifold. This tube is 6 inches 
in diameter and the ends are usually made slightly tapered 
mouth shape, so that they will fit snugly over the sleeves 
used in connecting two lengths of tube together and the 
manifold fitting where it is held securely in place by a thor- 
ough wrapping at two points with marlin, friction tape or 
elastic bands. The manifold having been connected to 
the cylinders and the inflation tube to the manifold and the 
bag to be inflated, the operation should continue as follows : 
See that the bag or balloon is properly spread out and folds 
made so as to avoid friction and the inflation tube which 



INTERIOR INSPECTION BALLOONS AND AIRSHIPS 245 

extends under the balloon properly cared for by placing sand 
bags about every 15 inches apart, staggering them on either 
side of the tube to prevent checking. Open the valves in the 
manifold branches. Purge inflation tube. Open main mani- 
fold valve. Open valves on the gas cylinders (flasks). Open 
valves gradually. When cylinders are considered to be empty, 
wait two minutes, then shut main manifold valve. Second 
shut valves on manifold branches, third shut valves on flasks. 
Disconnect and connect up to the next series immediately be- 
low, and continue as before. Watch manometer valve for pres- 
sure of gas in balloon, and when the desired pressure has 
been reached close valves as before mentioned, but do not 
disconnect until a suitable time has elapsed in which to note 
whether any serious leaks from valves or otherwise have 
occurred. When satisfied that all is well and pressure remains 
steady then disconnect. First tie the inflation tube (appen- 
dix) with marlin, elastic or friction tape, then all valves at 
manifold having previously been closed disconnect. The 
inflation tube is then rolled up slowly from one end, the other 
being open to allow the gas to escape. Caution: Never 
open the valves on flasks unless connected to the manifold 
for inflating, for if the flask is empty air will enter the flask. 
A very slight opening of the valve to a cylinder will prove 
whether it contains gas or not, and the valve should be 
immediately closed tightly. Other precautions : when about 
to start gassing a balloon in a hangar doors should be 
opened. No smoking within 150 feet of the operation, 
and no fire or open flame should be allowed in vicinity of 
the operation. Persons should not be allowed to loiter 
around near gas connections. Open sand bags should be 
distributed about and along the entire length of the inflating 
tube so that sand may be used to prevent fire spreading to 
or from the balloon by immediately dumping the sand on 
the tube or have inflation tube run under sand hopper that 



246 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

can be dumped quickly. See that all manifold connections and 
flask connections are free of sand or other particles that may 
cause a spark by friction. Also, a spark may, in very 
warm dry weather, fly or jump from a person to any of the 
above parts mentioned that may become charged through 
friction. This also applies when valving a balloon in hangar. 
Persons should not be allowed to be closer than is absoutely 
necessary to operate the valve. Have fire extinguishers 
handy. Another precaution should be to wet the ends of 
the hose or inflation tube when it comes in contact with a 
metal sleeve, and in very dry weather it would be well to 
drive a metal bar or pipe into the ground and connect 
the cylinders to it, thus making a ground. 

Q. If a balloon is in a hangar and she is being valved 
through one of the valves how far must a person remain 
away from this valve in order not to cause a static con- 
nection? 

A . In order not to cause a static connection when valving 
from one of the valves of a balloon while in a hangar, it is 
best that the person or persons remain at least 6 feet away 
from the valve. 

Q. If it is necessary for him to be inclose proximity to 
the valve what must he do in order to prevent a spark 
jumping from his body to the valve? 

A. If necessary for a person to be in close proximity or 
to touch the valve, or any other metal parts of a balloon that 
is inflated, they should first touch the fabric of the balloon, 
thus grounding themselves. This, it is believed, will pre- 
vent sparks jumping from the body to the valve or other 
metal parts which may be highly charged. 

Q. What is a finger patch and for what purpose is it 
used? 



INTERIOR INSPECTION BALLOONS AND AIRSHIPS 247 

A. Finger patches are made of rope and rubberized 
fabric. An eye is formed in the middle of a piece of rope, 
in which a thimble or a ring may be inserted; the ends of 
the rope are frayed out to suit the number of fingers to the 
patch; if four fingers, two pieces of rope are used, if six fingers 
three pieces of rope. The ends are frayed and cemented 
between two thicknesses of fabric and well sewed. Another 
and stronger piece of rubberized fabric is fitted over the eye 
and cemented to the first. This is the outer surface of the 
finger patch. The ends of the rope having been frayed and 
divided into equal parts, cemented and sewed, the patch 
is then trimmed and resembles in a way a human hand of 
4 to 6 fingers. The finger patch is used principally to 
distribute the load to as large an area of the balloon fabric 
as is possible. Used for suspension cables and handling ropes, 
also car and anchorage suspension, in fact, for most all 
connections to the bag of an airship. In a kite balloon the 
rigging (belly band) takes place of finger patches. 

Q. How is a car connected to an airship and by what 
means? 

A. A car is connected to an airship by means of fore and 
aft suspension cables, also thwart-ship or transverse suspen- 
sion cables, These cables connect by means of wire splic- 
ing into the eyes of the finger patches, or by shackles and 
turnbuckles to finger patch and to car. The car suspen- 
sion (C type airship) consists of some fifty finger patches, 
each of which is tested to withstand a pull of 2000 pounds. 
This type of rigging secures a very high safety factor and a 
considerable saving of weight over the belly band system. 
The location of the car is learned approximately from the 
blueprints, and when the car is lined up and weighed off the 
cables that are to be permanently spliced in connection to 
the car or at an equalizing ring or junction are spliced. In 



248 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

the preliminary set up these wires are clamped in place. 
After the splices are made they are wrapped with wire and 
soldered, and in places where this type of connection is likely 
to rub or chafe the balloon fabric chafing patches are provided. 

Q. How much tension should be placed in the various 
wires which connect a car to an airship? 

A. The tension of all suspension cables should be in accord- 
ance with the tension diagram. A Larsen Tension Meter or 
some other reliable instrument should be used in order that 
undue strain is not put on individual cables, causing an 
excess strain on the finger patch to the extent of wrinkling 
the balloon fabric in the vicinity and especially about the 
patch. Tail droop is usually caused by too much tension 
on the rear ropes and makes the ship very hard to manage. 

Q. How long should the balloon fabric last, assuming 
that same has received reasonable care? 

A. It appears that the life of balloon fabric when well 
taken care of is from eighteen months to two years for bal- 
loons that have been in active service. It is believed that 
with good care and careful handling the life of a balloon 
fabric may be from two to three years. The method of 
storage of balloons now in use is at present not satisfactory, 
due to deterioration, in from six to eight months, considerable 
work has to be done before the balloon can be put in service. 
But until a better method is adopted the following should 
be observed. The bag being properly folded and covered 
with canvas cover for same (should be dry and cool when 
folding for storage) should be placed in a dark room of mod- 
erate temperature, dry, and suitable for warming in winter 
months; the wood parts should be kept dry but not too hot. 
Sunlight has a destructive influence on rubberized fabric, 
and balloons should not be left in the sun longer than is 



• 



INTERIOR INSPECTION BALLOONS AND AIRSHIPS 249 

absolutely necessary. Suspension cables and metal parts 
should be protected to prevent rusting. 

Q. Of what kind of material is the rigging rope made of 
that is used in the free balloon, kite balloon and airship? 

A. The material used in rigging ropes of a free balloon 
is made up of manila, also Italian hemp. The manila is 
hard laid and used mostly in American made balloons, 
while the Italian hemp is loose laid and soft in texture. 
The manila rope resists mositure to a certain extent, while 
the Italian hemp absorbs moisture freely, thus adding to 
the weight carried by the balloon, especially in damp, 
foggy and rainy weather and tends to fray out. The kite bal- 
loon also carries some rigging made up from steel wire, in the 
form of bridles for the purpose of anchoring the balloon, also 
for handling from a winch either on land or on board ship. 
Airships are almost completely rigged with steel wire cables in 
the form of suspension, anchorage and control cables. Also 
sections of handling lines are made up of wire cables to which 
manila or Italian hemp may be attached by reeving through 
the eye in the lower ends of these parts. A log line, or more 
properly speaking signal halyard, is used in all types of 
balloons for valve cords and rip panel cords. A manila 
hemp drag rope is also used in balloons. 

Q. What is placed in the nose of a non-rigid airship to 
prevent same from collapsing from excess pressure in the 
nose when being driven through the air? 

A. Box type battens are used on all non-rigid type air- 
ships in the nose. These battens are built up of spruce and 
veneer and are hollow in the interior, the length of the longest 
batten being approximately 12 feet, width 2| inches, thick- 
ness li inches, with filler blocks of \ inch spruce, spaced 
about 12| inches apart, the sides being enclosed with J inch 



250 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

spruce. These battens are held in position by patches which 
are cemented to the envelope battens being laced to patches. 

Q. What kind of fabric is a balloon made of? How 
many plies? 

A . Balloon fabric of 2 and 3 plies rubberized, and manu- 
factured according to Navy Department's specification 113 
and 14-B is used in making balloons for the Navy. Two- 
ply fabric with the warp of one ply running at an angle of 
45 degrees to the warp of the other ply, with a gas film 
between, is used for the manufacture of kite balloons of the 
"R" and "M" types. The outside of the fabric is covered 
with a rubber compound which acts as a weather proofing. 
The finished fabric weighs about 9.5 ounces per square yard. 
Two- and three-ply fabric rubberized and with an inside 
proofing (rubber) in accordance with the specification men- 
tioned above and an outside proofing and aluminum, and 
with the inside and outside plies straight, the center or 
middle ply on the bias and a gas film between each ply is 
used for airships, the three-ply fabric being used especially 
in multiple engine types. Note the ballonet fabric is also 
a little lighter than the main bag fabric, both plies straight. 
No compound on either side. There is, however, a gas film 
between the plies. 

Q. What is a manometer gauge and what does it des- 
ignate? 

A . The manometer gauge consists of a glass tube mounted 
between two brass tubes. The brass tubes are connected 
at the top and bottom and with the manometer tube at the 
top so that the gas acts on both tubes. The glass tube 
connects with the brass tubes at the bottom and has a vent 
at the top for opening it to atmospheric pressure. The 
column of liquid in the glass tube, therefore, has the gas 
pressure in the balloon acting on one side of it through 



INTERIOR INSPECTION BALLOONS AND AIRSHIPS 251 

the brass tubes and atmospheric pressure acting on the other 
side through the glass tube. The reading on the scale is 
therefore the difference in pressure between the pressure 
in the balloon and atmospheric pressure. The scale is placed 
over the brass tubes and bent back behind the glass tube and 
is graduated to read the pressure directly in inches of water 
when manometer liquid or colored kerosene is used in the 
manometer. Shows gas pressure in the balloon or air pressure 
in the ballonets. 

Q. If a balloon having ballonets is kept inflated all 
night, which do j^ou consider best, keep ballonets inflated 
or not inflated? 

A . It is considered that the purity of the gas in the bag 
at all times is of more importance than the cost of the gas 
required to keep the bag properly inflated. Therefore, if 
possible I would not keep the ballonets inflated with air, 
because the air penetrating from the ballonets into the gas 
bag would considerably reduce the purity of the gas, thereby 
necessitating the purging of the gas bag more often and at 
greater expense than it would cost to keep the pressure 
up by inflating the main bag with gas. 

Q. How are the seams secured together in a balloon? 

A. The seams of a balloon are lap-jointed, cemented, 
double stitched and taped inside and out. The seams are 
usually \ inch to J inch lap with two rows of stitching J inch 
apart, 7 or 8 stitches to the inch. The shuttle stitch is used. 
One single ply fabric strip If inch wide of same color as exte- 
rior of envelope is cemented over extension of seam and one 
single ply raw white linen strip If inch wide is cemented 
over interior seam. The strip is coated with unvulcalnized 
rubber on the side next the seam, and over this is cemented 
another strip of single ply fabric 1| inches wide. This is 
rubberized on the gas side. In kite balloons the seam lap 
is only \ inch. 



CHAPTER XXXIX 
Method of Folding Balloons, Kites and Airships 



Q. Describe the methods of folding free balloons, kites 
and airships. 

A. Free Balloon — Folding Up for Storage. The balloon is 
pulled out straight with the valve hole at one end and the 
appendix at the other. The seam containing the rip panel 
slit is laid out straight on the ground and the rip panel in 
place, if the balloon has been ripped. Each panel is folded 
in the middle and the meridian seams laid on top of one 
another. The entire balloon now lies on the ground in a 
long strip and tapering to the valve hole at one end and the 
appendix at the other, resembling a flattened orange peel. 
The reason for placing the rip panel in this location is to 
facilitate repairs. For a similar reason in wrapping up this 
long strip the start is made at the appendix and the valve 
hole and rip panel is rolled on the outside of the bundle. 
Thus, it is necessary to unroll and unfold but a small 
portion of the balloon for the insertion of the rip panel. The 
balloon is now rolled in its packing case and placed in the 
basket, everything having been previously removed from the 
basket, also valve and any other movable wood or metal parts 
which may damage the balloon fabric when wrapping it for 
storage. 

Kite Balloon. Fold a kiteballoon after the removal of detach- 
able parts as above mentioned for free balloon, and wrapping 
all fixed metal parts such as steel wire, cables, etc., in a 
canvas or old rag covering to protect the fabric, first greasing 
the parts to prevent rust and deterioration. In some cases 
bags are furnished in which many parts attached to the 
envelope can be placed and same rolled up in the main bag, 

252 



FOLDING BALLOONS, KITES AND AIRSHIPS 253 

while others are placed separately in the trunks furnished for 
the complete balloon. The car or basket suspension made 
of hemp and fitted to the belly band can and should be 
removed from the envelope before folding for storage for any 
length of time, as mildew may occur and rot the cordage and 
damage the fabric. Also see that all fabric is clean, dry and 
cool when folding. Never fold in sun if it can be avoided. 

Airships. In folding an airship : The car having been dis- 
connected and the rudder, fins, elevators, nose battens, 
valves, scoops, gravity tanks, in fact all movable wood and 
metal parts as well as suspension cables, bridles and control 
wires, and those not removable inside and out have been 
properly greased and wrapped with burlap, cotton cloth or 
canvas to protect the fabric; the balloon is then laid out as 
before mentioned, the nose at one end and the tail at the 
other; the fabric is folded in a long strip one section wide and 
the full length; if possible, let the envelope lie for three or 
four hours and much of the gas or air which was not driven 
out up to this point will slowly work itself out. The cables 
or ropes which were not detached, owing to their being 
spliced permanently into the finger patches, are laid out 
smoothly between the folds the long way, so that they will 
fold or roll up without injury to the fabric. When the 
envelope has settled down due to the escape of the air 
through the various openings, start rolling the bag from the 
nose to the tail, forcing out all remaining gas through the 
appendix in the tail. Put on cover and store in the trunk for 
same, and put same in dry, cool, dark place. If such a 
place can be had, and is large enough to permit of storing 
the envelope in one long strip wrapped in the ground cloth 
for same without the rolling, it is believed the life of the 
fabric would thus be prolonged, as folding and rolling airships 
that have been doped is cause for cracking and breaking of 
the dope film, necessitating redoping before the airship en- 
velope will give satisfaction. 



CHAPTER XL 

Structural Inspection 

Q. What inspection would you make from a structural 
standpoint before pronouncing any of these balloons ready 
to take the air? 

A. Before pronouncing a free balloon ready to take the 
air: Examine thoroughly all parts, wood, metal, rope and 
fabric ; the net with its crows feet suspension to the suspension 
ring; the basket (car) structurally, also main suspension ropes 
that pass through and under the fibers up to the suspension 
ring; toggles and eye splicing as well as the harness cord 
wrapping over some or most of these splices; the gas valve, 
ring, seat, gasket, springs, yoke, etc., the valve cord, the rip 
panel and cord, the appendix ring, appendix draw string and 
valve cords properly measured off and arranged handy for 
operator. See that the basket is attached to the car with 
the long side under the rip panel; attach basket to suspension 
ring so that drag rope will be on the proper side. Balloon 
should be fully inflated. 

Kite balloon should be given a similar inspection as given 
the free balloon with a further inspection as follows: Inspect 
set and test gas valves, gas valve to open automatically 
when ballonet is empty and gas pressure 1.6 inches according 
to manometer. Examine lobes and lacing and openings be- 
tween them to ballonet, air scoop to ballonet, winch sus- 
pension V wires, rigging band (belly band) and finger patches, 
handling wires and the cable to the winch which is to let the 
kite balloon out and hold or haul it down as desired, also the 
telephone cable which is in the center of the kite cable and 
its connection to the kite basket set and the winch. Should the 

254 



STRUCTURAL INSPECTION 255 

balloon not balance properly the proper balance can be 
obtained by means of changing the fore and aft suspension 
until the balloon rides at the desired angle. 

Inspection of an airship: Check the alignment of the car 
with the fore and aft axis of the balloon by dropping a line 
from the nose and one from the tail. Mark the center of 
buoyancy on the car from blueprint and check distance from 
nose. Check the distance from top of car to bottom of 
balloon which should be as called for on plans. Examine all 
ropes, wires and cables for soundness as well as fittings, 
turnbuckles, shackles, rings, thimbles and eye splices. With 
1 inch pressure in gas bag note whether there is any tendency 
to buckle or droop. This may be due to undue stress on the 
fore and aft suspension. Examine rudder and elevator for 
clearance from the bag and freeness, smoothness and positive- 
ness of action, and that with 1 inch pressure in the bag, the 
controls to be reasonably taut. Examine all finger patches ; see 
that they are in good condition and the pull on each is evenly 
distributed. Examine, set, and test the air and gas valves. 
Gas valves should start to open automatically at 1.6 inches 
as shown on the manometer, the air valves at 1.3 inches, 
when the gas pressure in the main envelope is to be carried 
as 1 inch. Examine the ballast tanks and valves, also cords 
to same. Examine the nose battens and fins, fin braces, 
and see that the fins lie on center line of patches except 
lower vertical fin which is offset to overcome torque on a 
pusher type ship. The longer wire of each pair of braces should 
be put above the side fin so as to give the fins a droop of 2 
to 3 inches at outside edge. See that the V-wire on bridle and 
connections of the drag rope are in perfect condition. All 
pulley leads and wire where it passes over them should be 
examined. See that all metallic parts that come nearer than 
six feet to each other are electrically connected. Balloon full 
of pure gas properly balanced should trim on an even keel 



256 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

with the power off and a full load in place. See that there 
is at least a two inch take up in the rudder wire reels 
on the rear foot bar. See that dampers work and are tight, 
alsothat scoops can be raised or lowered. The pontoons 
inflaed and properly secured in place; all instruments in placa 
and securely fastened; the car frame wires and fittings 
inspected for soundness, rigidity. See that sea anchor and 
cable are in good condition and the cable properly made fast 
in the nose and led aft to the car and secured. 

Q. What factor of safety has an airship when the manom- 
eter tube reads 1J inches? 

A. When the manometer tube reads 1 to 1J inches the 
usual safety factor is about 8 if envelope is new. 

Q. What is the weight of hydrogen gas and air? 

A. Hydrogen gas weighs approximately 5 pounds per 
1000 cubic feet and air approximately 75 pounds per 1000 
cubic feet. Weight of one cubic foot of air at 30 inches 
pressure (Mercury) and 70°F. 0.075. Weight of one cubic 
foot of hydrogen gas at 30 inch pressure 70°F. 0.005. 

Q. What rule is there for determining the length of a drag 
rope of a free balloon, kite balloon and airship? 

A. The method for determining the length of a drag rope 
is to multiply the diameter of the balloon by 5 and add 60 
feet to this. This is approximate. 

Q. What is an appendix, and for what purpose is it used 
on the three types of balloons above mentioned? 

A. The appendix of a free balloon is a tube or alcove made 
of rubberized fabric, its length and diameter being in accord 
with the size or volume of the balloon. A 19,000 cubic foot 
free balloon has an appendix about 15 inches in diameter and 



STRUCTURAL INSPECTION 257 

about 5J feet long. A kite balloon is fitted with the appendix 
in the bow just below the nose. It is large enough to permit 
men to enter the bag. It is also fitted with an inflation tube 
which after inflating the bag can be rolled or folded and 
placed in a pocket about the appendix, and the flap buttoned 
down. The tube is securely tied with a rubber cord or tape 
around a rubber core to prevent gas escape. An airship is 
fitted with two appendixes, one underneath and just forward 
of the after ballonet about opposite center of the car, and the 
other under the tail of the balloon. Used for entering 
balloon for work or inspection, also for inflation purposes. 
IMade of rubberized fabric reinforced at junction of envelope, 
and taped over all joints. In addition to the appendix above 
mentioned for a free balloon, kite balloon and airship, there 
are fitted other and smaller appendixes for the various valve 
cords, rip panel cord, etc. These are cemented and originally 
sewed to the bag and taped at joints, fitted with rubber cores 
through which the cores pass and afterwards taped to prevent 
leaks. And in a kite balloon the rear appendix in some types 
is led in through the vertical lobe to the tail of the balloon 
for inflating the upper lobes. In a free balloon the appendix 
is located at the opposite side of the bag from the valve, 
which in the case of free balloon is the bottom; kite balloon 
nose and tail; airship bottom about one-third distance from 
nose and under the tail of the bag aft of the rudder. On 
airships appendixes are called inflation sleeve. The princi- 
pal use of the appendix in a free balloon is to permit equal- 
izing the pressure inside and outside the balloon, and its 
length prevents air getting into the bag and gas getting out 
except by expansion and contraction. The length is also 
governed by the strength of the fabric of the balloon. 

Q. Which do you consider the best ballast, sand or water? 
Why? 



258 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. Water, if the equipment is such that the water ballast 
can be released in sufficiently large quantity to be of service 
in checking the descent, otherwise sand. 

Q. What special inspection would you make in connection 
with the rudder on an airship? 

A. The rudder in addition to the inspection for soundness 
of its members should be examined for clearance of the bag, 
free and smooth as well as positive movement, that the 
hinges, pins, horns and braces are in perfect condition and 
that the rudder control cables should have no sag in them. 

Q. Describe static electricity, and how it is induced in a 
balloon. 

A. Causes of sparks which ignite the hydrogen seem veiy 
obscure, although there are various theories put forward. 
The passing of dry gas over metal surfaces does in some cases 
cause the metal to become charged with electricity, and at 
times a fairly large spark can be obtained by bringing two 
such objects together. Compressed hydrogen is dry and it 
seems possible that the valves of the flasks become charged, 
due to the rapidity with which the gas passes through them, 
so that if the tube is blown suddenly off the valve, a spark 
may occur which would ignite the hydrogen. It is also 
believed that a person's body may, in dry weather, become 
so charged that when coming in contact with another body 
or the valve or any part of a balloon so charged, cause a 
spark, and if valving a balloon may, if closer than 6 feet, be 
the cause of an explosion and perhaps the destruction of the 
balloon. It is also stated that it is possible to cause this 
spark by rubbing the inflation hose or tube, or the balloon 
itself, in taking it into or from the hangar, both being charged. 
An airship may become highly charged while passing through 



STRUCTURAL INSPECTION 259 

the ail* at a high speed, especially if there are particles of 
dust, smoke or mist; with ordinary air the effect is small 
with vessels with a speed below 60 miles per hour. The 
hydrogen gas may issue from a valve with sufficient speed 
when gassing to charge the rubber gasket of the valve seat 
and cause a spark to pass through the gas to the valve. This, 
however, may be prevented by coating the rubber ring with 
graphite or by connecting the valve and the seat by a wire 
fastened to each. 

Q. Describe a kite balloon winch, and what is necessary 
for its upkeep? 

A. There are three types of N. C. L. kite balloon winches, 
in all three of which the cable handling mechanisms are 
similar but which differ primarily in their form of power 
plant, viz: (1) gas engine used chiefly for shore stations and 
motor trucks; (2) steam engine for destroyer service; (3) an 
electric motor used mainly for battleships. The N. C. L. 
Engineering Corporation of Providence, R. L, furnishing the 
gas engine type for shore stations and battleships. The gas 
engine types are equipped with 8 cylinder Herschell-Spillman 
motors which drive the winch unit through Entz magnetic 
transmission. The electric types are equipped with motors of 
the General Electric Company's "CO-1800" line, are of the 
totally enclosed series wound type and have an intermitter 
rating of 50 horse power at 725 R. P. M., based on a 55°C. 
temperature use. Requirements: Shall be capable of exert- 
ing a maximum pull of 6000 pounds on balloon cable. Haul 
in at a maximum speed of 400 feet per minute against a 
2000 pound pull on cable. Haul in at a reduced speed at any 
pull of 2000 to 6000 pounds. Pay out, maximum speed of 
1000 feet per minute. Pay out at a speed of not more than 
150 feet per minute against a dynamic breaking effect with 
a pull of 2000 pounds on cable. Smooth stopping and start- 



260 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

ing must be obtained under all conditions of load and speed. 
The functions of a kite balloon winch are : Hauling down 
the balloon, paying out the cable when the balloon is ascend- 
ing and holding it when it is aloft. The cable serves two 
purposes — it holds the balloon and carries the inner core of 
an electric telephone cable, whereby communication can be 
carried on between the kite and the ground or ship. Care 
must be taken not to kink or make sharp angle turns with 
this sort of cable, as the telephone cable may be destroyed. 
There is a main drum which carries the f inch cable generally 
used. This type of cable should never be reeled up under a great 
strain, and to prevent this a system of two surge drums with 
one, two, three and even four additional single sheaves is 
used, the drums and sheaves being grooved deep enough to 
carry the cable with little chance of it jumping out of the 
grooves. The main drum (called storage drum) is located 
on the frame or base of the winch and in front of the engine, 
the surge drums on the left hand side of the storage drum 
and engine and directly connected so that these drums take 
the load coming on the cable and gradually reduce it until 
when it reaches the storage drum there is only sufficient pull 
on the cable to make it lay in smooth coils about the drum. 
There is also a leading swivel block directly in front of the 
surge drum with two sheaves over which the cable passes 
before it reaches the surge drum. This swivel block with 
one sheave in each end of it serves to keep the cable in control 
at all times, no matter which way the kite may be from the 
winch. When the cable leaves the surge drum it passes 
around a large horizontal sheave directly under the lower 
surge drum to another sheave, running with its axis the 
same as the large storage drum and which works back and 
forth on its axis, thus regulating the coils of the cable on the 
storage drum under a light tension. The two surge drums 
are about 12 to 14 inches apart and the center of the axis of 



STRUCTURAL INSPECTION 261 

the two drums are on a line about 60 degrees from the base 
of the winch. The operator stands or sits directly in rear 
of the surge drum, feet on pedals and hands on levers, facing 
the surge drums. There is a graduated cable indicator which 
gives the number of feet of cable paid out attached, also a 
tension indicator for registering the pull in pounds on the 
cable while the kite is in the air or being held near the ground. 
The care and upkeep of a kite balloon winch is similar to that 
exercised on board ship for steam and electric winches and 
cranes. 

Q. How is communication maintained with a kite balloon? 

A. By making the necessary telephone connection at the 
winch end of the cable, which has an electrical telephone 
cable as its center core, and the kite end of this same cable. 

Q. What would be the percentage of diffusion of gas in 
twenty-four hours that would warrant the re-doping of the 
envelope? 

A. As the diffusion of a new bag is about 0.2 of 1 per cent 
in twenty-four hours, it is believed that a diffusion of 5 to 10 
per cent in twenty-four hours is sufficient reason for redoping 
the envelope. 

Q. What should be the maximum permeability of balloon 
fabric? 

A. The maximum permeability per square meter for 
twenty-four hours on new balloon fabric should not exceed, 
for three-ply envelope balloon fabric as used for C and D 
class airships, 15 liters. 

This maximum permeability applies also for airship fabric 
used for ballonets, two-ply, in B, C and D class airships and 
R and M type kite balloons. 

Q. What is the difference in the weight of a cubic foot of 
water and a cubic foot of sand? 



262 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. A cubic foot of fresh water weighs 62.5 pounds, salt 
water 64 pounds, dry sand about 103 pounds. Difference 
about 40 pounds per cubic foot. 

Q. What is the usual weight of a bag of sand ballast? 
A. The usual weight of a bag of sand as used in connec- 
tion with balloon work for ballast purposes is 30 pounds. 

Q. What are. the dimensions and of what material is a 
sand ballast bag made? 

A. Sand bags are made up of about No. 6 canvas. Lap 
seams and double stitched, with a 1 inch strap on the bottom. 
The bag is 9 inches in diameter and about 12 inches high from 
bottom seam to center of eyelets, there being eight eyelets 
spaced around the top hem for the purpose of reeving a draw 
cord to close the bags when filled with 30 pounds of sand, 
also for the purpose of suspending the bag to the net or other 
parts of the balloon when inflating. 

Q. By what means are side valves in a kite balloon or an 
airship operated automatically? 

A. The side valves in a kite balloon and airship are 
usually of an automatic type, which can be set to open at a 
desired pressure from within the bag by the means of an 
adjusting gear connected with the mechanism of the valve. 
This is especially so in the case of a gammeter valve, which 
is the type of valve used at present in all but free balloons. 
In some of the older type kite balloons a system of cord 
connection from the valve in the nose of the balloon to a 
patch in the tail, with a vertical cord from this down to a 
spider of eight cords each, anchored to a patch cemented to 
the diaphragm of the ballonet and connecting at a point 
representing the apex of a cone. The cord is so adjusted 
that when the balloon is nearly completely inflated with gas, 



STRUCTURAL INSPECTION 263 

the ballonet becoming flattened out against the envelope and 
the pressure of the expanding gas causes the balloon to 
increase slightly in diameter; this combined effect puts a ten- 
sion on the cord and opens the valve allowing the gas to escape 
until the pressure is normal when it automatically closes as 
the tension on the cord decreases. Forward opening star 
valves are also used on kite balloons, M type. 

Q. What is the nearest distance a person smoking would 
be permitted in the vicinity of an inflated balloon? 

A. When a balloon is being inflated, no smoking, open 
fires or lights should be permitted within 150 feet, and no 
open fires should be permitted in vicinity of a balloon when 
inflating. 

Q. What is a hydrogen flask and of what material is it 
manufactured? 

A. A hydrogen flask is a cylindrical seamless steel con- 
tainer, 8 inches inside diameter and 4 feet and 3 inches high 
without valve or cap. Made of steel conforming to specification 
No. 3A and Navy Department specification No. 65Cl0a,Febru- 
ary 1, 1918. Chemical analysis carbon0.55, phosphorous 0.04, 
sulphur 0.05. Physical: elongation not less than 10 per cent 
on 8 inches test specimen. Elastic limit not more than 70 
per cent of the tensile strength. The bottom is slightly 
concaved, the top drawn to a neck and fitted with a malleable 
iron neck ring and threaded (outside) for a 3| inch diameter 
cap, and inside with a j-inch pipe tap, 14 threads to the 
inch, with a f-inch taper per foot. This neck ring is stamped 
with the name of the bureau concerned. Each container is 
fitted with a controlling valve of a type approved by the 
bureau concerned. The valve has a i\ inch outlet at right 
angles to the vertical axis of the valve, and is threaded with 
a special machine thread 14 threads per inch. Outlet threads 



264 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

of hydrogen shall be left hand 0.830 inch O.D. The walls of 
the cylinder are 0.23 inch. Capacity 2600 to 2700 cubic 
inches weight 110 to 120 pounds without valve or cap. Cap 
weighs 3 pounds, valve about 1 pound. Valve is also fitted 
with a suitable safety device (disc) which will rupture at 2500 
to 3000 pounds per square inch, tested by the Bureau of 
Explosives. 

Q. How many cubic feet of hydrogen are contained in 
this flask and what is the weight of flask and. hydrogen 
combined? 

A. A hydrogen flask contains from 180 to 200 cubic feet 
of hydrogen gas when charged under a 1800 pounds pressure. 
The weight of the container is from 110 to 120 pounds. It 
is impracticable to tell whether a container has gas or not 
by weight as hydrogen gas only weighs 0.005 per cubic foot 
and 200 cubic feet would only be one pound. 

Q. How is hydrogen put in the flask at the place of 
manufacture? 

A. Hydrogen is put in flasks at place of manufacture by 
means of compressors. The flasks are connected up to a 
manifold and the compressor takes the gas from the holder 
and drives it into the flasks under a pressure of 1800 pounds 
per square inch. 

Q. Is the purity of the gas lowered by putting same in a 
flask? 

A. The purity of the gas is not lowered by putting it in 
flasks if the following precautions are taken: First open valve 
of flask slightly to see if same is empty, if not, recharge, if 
empty. Connect up and charge to 200 to 250 pounds, then 
disconnect and allow the flask to empty; connect up again 
and repeat the operation, being careful to close the valve 
immediately the flask is empty, which is when it almost stops 



STRUCTURAL INSPECTION 265 

escaping through the valve. Close valve and connect up 
for the final charge which is 1800 pounds. 

Q. What color paint is marked on a flask to designate 
that it contains hydrogen? 

A. Hydrogen flasks are painted black and have a white 
band 6 inches wide painted around the flask, the top edge 18 
inches from the neck ring. 

Q. How much pressure will a hydrogen flask withstand 
without rupture? 

A. Each hydrogen flask is subjected to an internal test 
of 3000 pounds per square inch. One of each lot of five 
hundred or less are tested to the bursting point, and they 
are not supposed to burst under 6000 pounds per square 
inch. The safety device fitted to the valve on hydrogen 
flask is supposed to relieve the pressure and allow the gas 
to escape, preventing explosions due to expansion of the gas 
in cases where cylinders are in a fire. 

Q. How many types of manifolds are used in connection 
with transfer of gas from flasks to balloons, and which is most 
generally used? 

A. There are two types of manifolds: (a) low pressure 
and (b) high pressure. The low pressure manifold is most 
commonly used. The low pressure manifold consists of a 
cylinder made of a section of pipe 5 J inches outside diameter, 
yq inch walls and 14 inches long. Screwed into the bottom 
are 10 nipples with 8-foot armored hose connections attached. 
Each hose is fitted with a cap nut which is provided in case 
fewer than 10 flasks are connected at a time. 

Q. WTiat precautions should be taken when inflating from 
flasks or recharging empty cylinders with hydrogen gas? 



266 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINE 

A. In connecting cylinders to a manifold for the purpose 
of inflation or for the purpose of compressing gas into the 
cylinder it is absolutely essential to the preservation of life 
and property that if the gas in question be hydrogen, cylinders 
containing any other gas be kept out from the manifold. If 
hydrogen is compressed with certain gases a violent explosion 
will occur. If in connecting up the manifold the gas in any 
of the cylinders is questionable, do not use the cylinder as 
it might contain a gas that will cause an explosion. Also be 
very careful to see that washers that are non-conductors of 
electricity are not used to make an air tight valve connection 
on the cylinder or the manifold. Static electricity is pro- 
duced by the friction of gas rushing through small openings, 
such as is found on the ordinary cylinder valve. If a non- 
conductive washer is used, the circuit to the ground is broken 
and a fire will occur. Also be sure that the cylinder is placed 
on a substance that is a conductor of electricity, for if it is 
not grounded the static produced by friction will have no 
escape and the result will be disastrous. 

Q. When a cylinder full of compressed hydrogen is insu- 
lated and the gas is blown out through a copper tube, may 
the cylinder become charged? If so, how does the effect 
depend upon the rate of discharge? Does the charge increase 
uniformly with time? 

A. Yes, it increases rapidly with the rate. Marked 
effects were obtained when the gas was discharged through a 
copper tube yq inch in diameter, at the rate of 4 cubic feet 
per minute. No, the charge does not increase uniformly 
with time. 

Q. Is a brush discharge as effective as a spark in exploding 
mixtures of hydrogen and air? 



STKUCTTJKAL INSPECTION 267 

A. It is believed that the discharge from the brushes of 
the wireless equipment is not as effective as the spark. 

Q. Is the balloon fabric used in the manufacture of air- 
ships a good insulator or not? 

A. Rubberized cotton fabrics such as are used by the 
Goodyear and Goodrich Rubber Companies are sufficiently 
good conductors, even when thoroughly dry, practically to 
equalize the potential of the whole balloon surface in about 
a minute. 

Q. Are the hemp ropes used in suspending the fuselage 
good insulators? 

A. No. From an electrostatic point of view they are 
good conductors when wet. 

Q. Are the rubber rings forming part of the Goodyear 
valve seat good insulators? 
A. Yes, when they are clean. 

Q. May an airship acquire an electric charge as a result 
of being driven through the air at high speed? 

A. Yes, if the speed is sufficiently great; rubberized 
cotton fabric becomes negatively charged while rubberized 
silk fabric becomes positively charged. Rubber when rubbed 
against cotton, silk or aluminum becomes highly negatively 
electrified. 

Q. What is meant by the term "lift" as used in connection 
with balloons? 

A. By the term "lift" is meant the difference between the 
weight of the balloon (including gas) and the weight of the 
supporting medium displaced, which is air. Lift is affected 
by the volume of the gas in the balloon, the purity of the 



268 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

gas, the barometric pressure of the air, the temperature of 
the air, and the humidity of the air. Quite naturally, the 
more gas the balloon contains the greater will be the positive 
lift. This is one reason for always having the balloon as 
completely inflated as possible, when at its working altitude. 
Lift as applied to kite balloons should be specified as to 
whether it is gross lift or useful lift. The gross lift is the 
total displacement of the balloon minus the weight of gas. 
The useful lift is the difference between the gross lift and the 
fixed weight of the balloon; while in an airship the gross 
weight includes the weight of the gas. 

Q. What is a leak detector, and for what is it used? 

A. A leak detector is an instrument used in locating leaks 
around valves and other openings in a balloon as well as 
the seams and the fabric itself. This instrument consists of 
a perforated nickeled plate mounted on a hardwood ring 
about 8 inches in diameter, with a disc made of a specially 
prepared clay or some other composition, placed back of the 
perforated plate, a delicate diaphragm with a movable hand 
which indicates a leak, but does not register the quantity of 
the leak. The hand indicating a leak will remain at the 
position to which it is forced by the leak until released by the 
opening of a small press valve. Very slight leaks can be 
detected when the instrument is carefully placed with the 
hardwood ring at the back against the fabric, so that the 
pressure of the leak will reach the disc. Only hydrogen gas 
will pass through this disc. The leak detector is made in 
two or more sizes. The 4-inch and 8-inch sizes are in use 
at Pensacola, Fla. 

Q. What is a mooring harness, and where and on what 
types of balloons is it used? Of what is it made? 

A. Mooring harness is fitted at the top of a kite balloon 
and is used to anchor the balloon, also for bagging down. 



STRUCTURAL INSPECTION 269 

This harness is made of heavy braided cotton tape securely 
cemented to the envelope in a zigzag manner along the first 
and second gores from the center line and practically the full 
length of the bag, and held by patches, and is covered over 
with a light fabric tape matching that of the envelope. To 
this harness sixteen picket lines are attached by means of 
drop forged steel rings. There are seven lines on each side, 
one on the nose and one at the tail, made of the best grade 
manila or Italian hemp, and are used for anchoring the 
balloon to the ground in windy weather. The ends of the 
lines are fitted with eyes for reeving the anchor lines through. 

Q. What is a junction piece and where is it used? In 
connection with what type of balloons? 

A. A junction piece consists of a piece of stranded wire 
cable running through two U-shaped hollow. steel tubes and 
having an eye or loop spliced in one end and a brass toggle 
spliced into the other. It is used as a quick means for 
connecting or disconnecting the metallic V-wires of a kite 
balloon from the main cable leading to the winch. The main 
cable is attached to the junction piece by means of a loop 
in the end of it, which is slipped over one of the U tubes in 
the junction piece. The toggle in the junction piece is then 
put through the loop in the other end and the complete 
connection is made. The above description covers the R 
type kite balloon. 

Q. What are furling ropes and to what are they attached 
in a kite balloon? 

A. Furling ropes are attached to the two side lobes of a 
kite balloon, four ropes to each, and are used for the purpose 
of deflating and furling the lobes when so desired in manceu- 
vering or anchoring the balloon. 



270 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. In what way does the mid-suspension differ from the 
forward and rear suspension in a kite balloon? 

A. The mid-suspension of a kite balloon differs from the 
forward and rear suspension in that it contains an adjusting 
block and shock absorber. The adjusting block is used to 
make the mid-suspension taut when the front and rear 
suspensions have been attached and the basket located where 
desired. The shock absorber tends to take up any sudden 
jerks due to swaying or nose dives. 

Q. Name some of the knots used in connection with the 
ropes and rigging of a kite balloon. 

A. Some of the knots and bends used in connection with 
rigging of a kite balloon are : Figure eight, reef, clove hitch, 
single and double sheet bend, Mans harness hitch, sheep 
shank, bowline, bowline on a bight, crown knot, lever hitch, 
timber hitch, picketing hitch, eye splice, and the thumb 
knot. 

Q. What are pickets, and for what are they used? 

A. Pickets are mild steel or iron stakes with an eye in 
the top end. The bottom is pointed with two spurs or screw 
wings which assist in keeping the stake in the ground. In a 
way a picket is similar to an auger but has only two wings. 
They come in various sizes and lengths from 18 inches up 
to 4 or 5 feet, used in mooring a balloon down to the ground. 

Q. How does helium gas compare with hydrogen gas, 
first, as to weight; second, as to lifting power; third, as to 
ignition from sparks from atmospheric electricity and radio, 
and fourth, as to cost of production? 

A. Helium gas weighs approximately 6 pounds per 1000 
cubic feet ; hydrogen gas weighs approximately 5 pounds per 
1000 cubic feet. Helium has a lifting power of approximately 



STRUCTURAL INSPECTION 271 

92 per cent of hydrogen or 64 pounds per 1000 cubic feet, 
and hydrogen 70 pounds per 1000 cubic feet. Helium is a 
non-inflammable gas, while hydrogen is dangerously explo- 
sive when mixed with air, in certain proportions. Hydrogen 
can be manufactured at a cost of from 5 to 10 dollars per 
1000 cubic feet, while helium at present costs from $55.00 to 
$60.00 per 1000 cubic feet to produce. 

Q. What is goldbeater's skin and for what is it used? 

A. A goldbeater's skin is the blind gut of an ox, and is 
used in lining fabric for gas bags of a rigid airship. A gold 
beater's skin is practically impermeable to hydrogen, but 
owing to the small area (about 8 inches square) of each skin, 
it is a very expensive material for this purpose. 

Q. What advantage has the airship over the airplane? 

A. The main characteristics of an airship are: (1) long 
endurance, (2) ability to carry heavy loads, (3) variation of 
speed, (4) reliability, by which is meant freedom from 
liability to mechanical breakdown during flight, (5) comfort, 
(6) security. An airship need not descend in unfavorable 
country even if the engine fails while the airplane must 
descend. The airplane, on the other hand, bases its claims 
on the following points: (1) high speed, (2) low cost of 
production as compared to airships, and maintenance, (3) 
ease of housing. 

Q. Describe in detail how you would prepare a parachute 
for use on a balloon about to make a flight? 

A. The parachute is laid out on the ground cloth prepara- 
tory to folding for packing in a container made of fabric and 
cone shaped, with a ring in the inside of the top to which 
the parachute is made fast with a 30-pound breakable cord. 
There is also an eye on the outside of the top for securing the 
container to the car or basket. In folding the parachute for 



272 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

packing it is flattened out on the ground cloth the width of 
two pleats, so that there is one cord at each edge and one 
in the center. Then take every other cord in hand allowing 
the one skipped to fold down between those taken in hand 
until you have an equal number of pleats on each side of the 
flattened section. Lay these folds down flat and straight on 
top so that you will have another full width section on top 
when complete. These two outer folds form a pocket which 
it is stated seems to catch the wind and cause the parachute 
to open quickly when released from the container. Set the 
container bottom up and secure the top of parachute to the 
ring, with the breakable cord mentioned, and fold or pack 
the parachute into the container by a series of accordion 
pleats; then continue with the cords coiling them in a clover- 
leaf coil, arranged so that any two coils of cords running in 
the same direction have a coil of cords running in another 
direction between them. Level off the top of the coil so that 
the suspension hoop will lay flat on top, and then secure it 
m place with four breakable cords which are made fast to 
the inside of the container. The four suspension ropes from 
the hoop are then coiled down on top of the hoop and the 
cover through which the suspension ropes lead is put in 
place and securely held by an elastic band around the edge. 
The junction of the four suspension ropes and the central 
rope to the toggle in the cover are close up to the cover and 
only the main suspension rope with hook in the end for 
attaching to the harness is left free. The parachute is now 
ready for attaching to the car or basket. 

Note: The above mentioned description applies to the general type 
of parachute carried in containers in airships. There may be a 
slight variation from the above description in some special type para- 
chute or some special precautions necessary to be taken, but as a 
general rule the above description covers the method of parachute 
packing in practically all cases where same is carried in a cone shaped 
container. 



STRUCTURAL INSPECTION 273 

Q. An airship is flattened out on the floor of the hangar 
for inflation. State in detail what precautions you would 
take with the vertical fin (upper stabilizer) and the horizontal 
stabilizer to keep them in place and prevent damage to the 
bag, the parts mentioned being strapped in place to the 
bag. 

A . The balloon being in a hangar and facilities available, 
a small tackle is rigged directly over the vertical fin and a 
bridle of six legs, two to the vertical fin and two to each 
horizontal fin, are led out and made fast to canvas straps 
placed about the fins so that they are balanced laterally and 
vertically. The forward leg to the vertical fin should be 
about 30 to 36 inches shorter than the rear leg in order that 
the forward end of the fin may be raised off of the floor ahead 
of the rear end as the bag fills with gas. The two legs to 
each horizontal fin should be about 3 to 4 feet longer than the 
rear leg of the vertical fin, as these parts are located on the 
bag at a point considerably lower than the vertical fin. The 
bridles should be made fast at the tackle so that there would 
be no slipping or surging, and any slight adjustment found 
necessary as these parts are lifted with the inflation of the 
bag can be made from a ladder at the bands about the fins. 
The brace wires to the fins are rove off with sufficient slack 
in them and set up later when the bag is fully inflated. 

Q. Are the wire cable controls to all valves on an airship 
connected direct to the metal part of the valves? 

A. No, the cables are made fast to a short piece of sennit 
line, which in turn is made fast to the valve. Also an elastic 
section about 16 to 18 inches long is secured to the valve cord 
in such a manner as to leave about 4 inches of slack in the 
control cable at the valve. This allows for tension on cable, 
due to expansion or stretch of the gas bag, without opening 
the valve prematurely. 



274 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. Describe in general details the difference in the kite 
balloons of the M and R types. 

A. The M and R types of kite balloons are practically 
the same in appearance, but differ as follows: The M type 
balloon (similar to the British type M) is of 32,800 cubic feet 
capacity, a length of 82 feet, and a maximum diameter of 
26 feet, and a ballonet capacity of 9358 cubic feet or 28J per 
cent of the volume of the envelope, and is placed in the after 
part of the envelope instead of forward as in the R type, 
and the air enters the ballonet through an opening com- 
municating with the rudder instead of through a scoop 
forward, as in the R type. The M rides at an angle of 8° 
to 12°, the R 3° to 4° from the horizontal. The suspension 
band is made up of one ply of canvas duck and several plies 
of envelope fabric to which are cemented and sewed individ- 
ual patches for each suspension point. The patches are made 
of one-inch herring bone tape, which has an ultimate 
strength of 300 pounds. Rope used in all rigging is of Italian 
hemp, and a movable or self adjustable rigging is provided 
by means of the aluminum pulley blocks used in the bridles. 
Due to the greater strength (50 per cent) in the Italian hemp 
over the Manila Yacht rope used in the R type rigging, the 
rigging of the M type has a safety factor of 18 or three times 
greater than that of the R type. The side gas valve in the 
M type is automatically operated by internal rigging, the 
valve being opened when the diaphragm of the ballonet is 
down to the lowest point, the ballonet being empty and the 
gas pressure rising. The R type balloon is of 37,500 cubic 
feet capacity, a length of 92 feet, maximum diameter of 27 
feet, the ballonet capacity 25 to 30 per cent approximate. 
The R type has a useful lift of 1229 pounds for pilots, instru- 
ments, cable and ballast, and that of the M type about 1084 
pounds. The R type rigging is made of Manila hemp and 
not self adjustable as that of the M and the side gas valve 



STRUCTURAL INSPECTION 275 

is of the gammeter type, automatic without the internal 
rigging; the maximum altitude attainable (feet) R 6000, M 
5000, working altitude R 4000, M 2500. It is believed the 
above figures are excessive, although claimed. 

Q. What is the stabilizer rigging of a kite balloon? 

A. The rigging inside the stabilizer by means of which the 
stabilizers are kept in their proper shape, consists of a 
series of two diagonally crossing lines and one horizontal line 
attached to the envelope and stabilizer by means of fabric 
suspension bands and suspension patches placed at intervals 
and permit of ready adjustment on assembly or after flight. 
The diagonal crossing lines are staggered to prevent chafing. 

Q. What is a suspension bar? 

A. A suspension bar used in kite balloon rigging is a 
horizontal bar made of ash or some other equally strong 
wood, to which are attached the "fore," "mid" and "aft" 
basket suspension lines, also six lines for attaching the bar 
to the basket. 

Q. What is a nurse tube and where located in a balloon? 

A. An auxiliary inflation tube entering the envelope at 
its lowest element just forward of the toe of the ballonet and 
extending along the outside and bottom of the envelope and 
thence to the basket. It is used in inflating (replenishing 
gas) from aboard ship when the balloon is in the air, thus 
avoiding the necessity of having to haul the balloon down 
on deck completely for the inflation through the appendix 
in the nose of the balloon. 

Q. What is a quick attachment coupling and where is i1 
used? 

A. The quick coupling is fitted to the basket end of the 
nurse tube which is connected to the main inflation line on 



276 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

board ship. It is made of bronze and is somewhat similar in 
construction to a fire hose coupling. The female end is 
permanently attached to the basket end of the nurse tube 
and the male end, provided with a metal sleeve 5 inches long, 
is kept on board ship available for attachment to the main 
gas inflation tube. The quick release or attachment coupling 
provides a means for reducing the time required for making 
connections during the inflation of the balloon through the 
nurse tube. The rubber gasket seat between the male and 
female parts forms a gas tight connection. 

Q. What is a check valve, how made and where used in 
a kite balloon? 

A. A check valve is located at the envelope end of the 
nurse tube and provides a means for automatically closing 
the inflation tube at the envelope after inflation. It consists 
of a 90-degree elbow made of aluminum with an open end 
outside the envelope for the attachment of the fabric nurse 
tube and a closed end inside the envelope. This closed end 
has a number of 1-inch diameter holes through it. A 
rubber elastic sleeve encloses the discharge end of the valve. 
During inflation this elastic sleeve expands and allows the 
gas to flow into the gas bag. After inflation the sleeve con- 
tracts and covers the holes, and thus checks the back flow 
of gas. This also eliminates considerable diffusion which 
would occur with the valve at the basket end of the nurse 
tube. 

Q. What is a discharge tube or hood and where is it 
located in a kite balloon? 

A. When the gas leaves the check valve at the envelope 
end of the nurse tube, it discharges into a loose fabric hood 
or tube which encloses the entire check valve and extends 
about 6 feet forward of the valve, is cemented to the envelope, 



STRUCTURAL INSPECTION 277 

and has about eight 3-inch diameter holes for allowing the 
gas to flow into the envelope. During inflation the gas 
pressure holds the fabric up to full form and allows the 
gas to discharge freely into the bag, and after the inflation 
ceases this hood collapses and the discharge holes are closed, 
thus forming a second check against backward flow of gas 
through the nurse tube. 

Q. What instruments are carried in a kite balloon? 

A. The instruments carried in a kite balloon are: Gas 
manometer, compass, anemometer, altimeter, binoculars, 
watch, telephone, and in addition to these pencil and paper 
for notes, also charts and maps. 

Q. What is the maximum pull on a kite balloon cable, 
also what is the breaking strain? 

A. The breaking strain of a f inch diameter 7 by 19 
stranded steel wire cable as used for kite balloons is 14,000 
pounds, and the maximum strain on it when balloon is in 
flight, even in a 60-mile per hour wind, is only about 6000 
pounds. 

Q. What are danger cones and for what purpose are they 
used? 

A. Danger cones consist of a small cone made up of 
fabric with a lanyard about 3 feet in length connected 
thereto. These cones are snap hooked about 300 feet apart 
on a kite balloon cable in order to warn heavier-than-air 
craft to keep clear of cable. The first cone, however, is placed 
800 feet below the balloon. Pennants are sometimes used for 
this purpose, but the cone is considered more desirable. 

Q. By what means are airships inflated? 
A. Airships are inflated through what are known as infla- 
tion appendixes, consisting of one, or generally two appen- 



278 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

dixes about 30 inches in length, to which the inflation hose 
is attached while being inflated, after which the appendix 
is folded and tied off to prevent leakage and pushed inside 
of envelope, and the flap which is secured to envelope is 
laced around the opening in the envelope. 



CHAPTER XLI 

Instructions for Putting in Service, Rigging of Cable 
and Operating N. C. L. Kite Balloon Winch 

The following operating instructions for N. C. L. kite 
balloon winch were furnished the Government by the manu- 
facturers of this type winch. 

Having installed the winch in position, the leading-off 
gear packed in a separate box may be assembled. First 
the double-tapered steel bar is inserted in the hole bored 
for it in the base. The keyway in the bracket should be at 
the outer end. A spot will be found sunk in one end of this 
bar and this spot should match up with the point of the 
set screw that will be found in the base about 14 inches 
directly back of the leading-off gear support boss. The 
leading-off gear itself is inserted in this boss and then the 
end bracket applied to support the outer end and both 
pinch screws tightened up. The stand should swing freely 
in this position. If any binding is encountered, it will be 
due to the outer boss being slightly out of alignment with 
the support boss on the base and correction may be made 
by rocking the steel bar carrying the support bracket very 
slightly by blows from a lead hammer. The next point 
in the installation of the leading-off gear is the attachment 
of the stabilizing spring, a stiff tension spring which will 
be found in the same box with the rest of the gear. The 
eccentric anchorage lever is provided in order to easily 
tension this spring. The bosses for its support are on the 
side of the base where the lever will be found already installed. 
The screw should be taken out of the small end of this lever 
and the lever rocked so that the pin projecting from the 

279 



280 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 






pivot boss is at the nearest point to the leading-off gear. 
The spring is then hung on this pin and the through pin 
in the leading-off-gear spring bracket passed through the 
other eye. Cotter pins are inserted and the tensioning 
lever rocked back into its permanent position stretching the 
spring. The screw should then be inserted to lock the lever 
in this position. 

Before an attempt is made to install a rope, the power 
plant should be tested for condition. In order to do this, 
the battery cover should first be lifted 'and the battery 
connected. Take off the starting crank bracket cap and 
have a man at the crank. This is probably necessary owing 
to the fact that the battery, having been shipped, is in a 
somewhat depleted condition while the engine is probably 
stiff owing to the same circumstance. Having the gasoline 
tank filled, fill the radiator, take the § inch pipe plug out of 
the head of the Stewart vacuum tank and put about a pint 
of gas in this tank replacing the plug and making sure that 
it is tight. Look at the oil indicator on the engine. There 
is a vertical wire with its end bent at right angles indicating 
on a pressed steel scale on the crank case just ahead of 
the flywheel housing on the right hand side of the engine 
(at the point nearest the driver's seat). This should read 
well up to the top of the scale. In the event of oil being 
required, use Mobile "A" or almost any good medium 
engine oil. Leave the magneto lever on the dash board in 
advance position which is coincident with open throttle 
position. Open the throttle about 1 inch on the quadrant 
and then after throwing the ignition switch over to the 
start position (the word "Neutral" means nothing on this 
switch and should never be used as a switch position), lift 
the latch of the controller handle and, with the hand brake 
applied to the winch, throw the controller lever forward one 
notch at the same time having a man on the starting crank 



INSTRUCTIONS FOR N. C. L. WINCH 281 

give aid. As soon as the engine starts bring the controller 
lever back to neutral adjusting engine levers for idling posi- 
tion in the usual way, replace the starting crank bracket 
cap and after a moment or two's running to warm up, 
leave the hand brake in set position and throw the con- 
troller by tripping the latch forward two notches. It will 
be found that the ammeter on the dash now gives a charging 
indication and that by adjusting the throttle lever this 
may be regulated. Carry the charging rate at about 
twenty amperes and charge the battery for half to three- 
quarters of an horn- at this rate in the meantime removing 
the vent plugs from the batteiy cells and watching for 
excessive gassing. If this latter condition is encountered, 
cut the charging rate to about ten amperes and carry the 
process until the hydrometer reading of the cells is 1.280. 
In the event of the cells seeming to have lost electrolyte, 
fill with distilled water and watch for gravity. As charging 
proceeds, it will probably be found that the battery can be 
fully charged in about an hour to an hour and a hah and 
it is strongly recommended that this procedure be under- 
taken as soon as the winch is installed as the process of 
putting a rope on occasionally demands the use of the 
reverse gear of the winch. This latter function is accom- 
plished from the battery. 

After the battery is in condition, it is well to operate the 
winch in general for a few moments in order to properly 
lubricate the cam gear and to make sure that everything 
is in order. In order to run the winch, release the hand 
brake and with the controller handle still in the outer posi- 
tion, bring the handle back gradually towards the operator. 
It will be found that the winch speeds up and that the 
high speed is the position when the handle is nearest the 
operator's seat. In the crossover notch is neutral position 
and there are five points between the two that give positions 



282 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

of decreased power but increased speed on the part of the 
machine. The notch into which the controller handle can 
be passed is a braking range, the maximum ability of which 
is on the neutral point of the controller. As the lever is 
drawn back towards the operator in this notch, the electric 
braking effect is reduced. In order to reverse the motion 
of the winch, the controller is moved to starting position 
without the hand brake being applied to the machine. 
For this battery driven reverse it is advisable to have motor 
stopped. 

To recapitulate, the following are the actions necessary 
to induce the various functions of the winch: 

To Start: Ignition switch to start position, throttle in 
lever on quadrant slightly forward of vertical position, 
ignition two-thirds from vertical position, hand brake on 
winch set, controller handle forward one notch by lifting 
latch. Engine having started, controller to neutral. 

To Charge: Hand brake set, controller handle moved 
forward two notches by lifting latch over each notch, charg- 
ing rate checked by ammeter on dash and adjusted by throt- 
tle lever to rate desired. 

To Operate Wirich-Haul-in Direction: Engine running, 
controller lever same slot as for starting. Lever moves 
back towards operator from neutral to high gear position. 
First notch gives maximum pull, minimum speed, the follow- 
ing notches giving increasing speed, decreasing pull. On 
high position, engine is running direct to winch except for 
slight magnetic slip. Practically all normal hauling is 
done with controller in high gear position, emergency condi- 
tions demanding more pull being secured by moving con- 
troller handle back. General speed of operation is entirely 
by engine throttle, foot pedal and hand lever as on an 
ordinary automobile. 

To Reverse Winch: Ignition switch to off position, con- 
troller to starting position, hand brake disengaged. For 



INSTRUCTIONS FOR N. C. L. WINCH 283 

this condition, the battery is operating the transmission as 
an electric motor and the reverse action is only necessaiy 
when taking off cable for inspection where it is not desired 
to change drums. The reverse is also necessary in getting 
altitude with a balloon when the pull reduces itself to a 
point below that necessary to take cable from the machine 
freely. Under these conditions, the winch should be re- 
versed until the altimeter gives the desired reading. 

To Pay Out: Controller moved into the left hand slot, 
hand brake set, rope tensioned, release hand brake and to 
secure increasing speed of pay out bring controller handle 
towards operator. Minimum braking is at the extreme 
position toward operator, maximum back to neutral position. 

To Reeve on Cable: Run winch until the spooling pulley, 
the large pulley mounted on the outside of the spooling 
cam, is at the outer end of its travel. 

Take out the two cap screws holding guard in place by 
means of its split cap. 

Take out the small guard wheel and the main guide 
sheave of the leading-off gear by turning the hand wheels 
and withdrawing the center pins. The hand wheels will 
stay with the gears and it will be found that the pins are 
forced out as the wheel is turned in a counter-clock-wise 
direction. 

The side plates should be given an occasional smart 
rap with the hand as the pin is withdrawn so as to eliminate 
binding from spring in the side plate. 

Take off the guards over the surge drums. It will only 
be found necessary to loosen the screws after which the 
guards may be rocked sufficiently to come off over the 
screw heads. 

Arrange the cable on a stand with a detail of men at the 
stand and a second detail at a tensioning rig made of two 
planks between which the cable is drawn. 



284 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Thread the cable beneath the main pulley, through the 
leading-off stand boss, under the loose pulley on the inside 
of the lower surge drum and then by successive wraps over 
and under the surge drums without crossing until the last 
groove is filled. 

Carry the cable back around the horizontal base sheave 
guarded by the seat support frame. It will be found that 
this sheave lifts vertically about \ inch sufficient to permit 
the cable to be dropped into the groove. 

Run the cable to the horizontal sheave at the spooling 
pulley; pass it around the main pulley and then over the 
drums leaving about an extra 12 inch of slack when a quarter 
wrap can be passed over the top of the drum.. 

Apply the spooling guard and tighten up the screws. 

After making sure that the cable is slack on the surge 
drums start the engine and run the winch without hauling 
cable until the spooling cam rider is about J inch before 
dead center. 

Put a wire wrapping on the cable about 8 inches from 
the extreme end. After this is done, pass the end of the 
cable through the slot in the drum head. Grip it by means 
of the two clamps. 

Cut away the steel wire of the protruding end of the rope 
leaving the telephone core exposed. Then strip the core 
and make a connection to the telephone rings by means of 
the small screws on the three vertical posts. 

Tighten up the cable between the spooling drum and the 
surge drums and then by loop pulling tighten the rope 
over the drums themselves and so to the temporary tension- 
ing device. 

Operate the winch at a slow speed when it will be found 
that the cable will spool smoothly. 

Each winch is shipped from the factory with a fifty tooth 
spooling gear installed which is usually the proper gearing 



INSTRUCTIONS FOE N. C. L. WINCH 285 

to correctly spool f inch rope. There are, however, to be 
found among the tools in the tool box gears having forty- 
nine, fifty-one and fifty-two teeth. If the fifty tooth gear 
spools too close, remove it and install a forty-nine tooth 
gear. If, however, it spools too wide, it is then advisable 
to install the fifty-one or fifty-two tooth gears as conditions 
may require. The installation of these gears is easily made 
as they are mounted on a pivoted plate rocked into position 
by the pinion bolt. When the end of this bolt is loosened, 
it will be found that the supporting plate can be rocked 
forward and backward so that correct engagement can be 
obtained. 

The instrument head contains dials, registering speed of 
intake and payout and amount of free cable. This latter 
dial can be reset to zero by unscrewing the cap at the back 
of the instrument housing and by turning the dial which 
is mounted on a light friction drive to its proper indicating 
mark before starting each run. This dial properly set at 
zero at the start of a run should return to zero when the 
balloon is brought down but there might be, owing to lost 
motion in the gearing necessary, a slight variation which 
can be corrected at any time. The Bristol self-recording 
gauge will give a permanent record of rope tension when 
desired. For this purpose, especially prepared smoke chart 
should be placed in the face of the dial and handled with 
great care until the desired record has been taken when the 
chart can be fixed by washing in the fixative which is shipped 
in a small can with each winch. 

Except in cases of extreme emergency sudden starting and 
stopping of the winch should be avoided. 

Always have cable at rest before starting to haul in or pay out. 



CHAPTER XLII 
Ballooning 

fundamentals of operation 

The following is part of a course given in the above 
subject at the Naval Air Station, Pensacola, Fla. 

A free balloon is controlled by means of gas and ballast; 
that is, a certain amount of reserve weight is carried called 
ballast which is lifted by a corresponding reserve gas. In 
order to ascend or to check a descending impulse, ballast is 
thrown overboard. To accomplish the reverse, gas is re- 
leased. The latter process is largely an automatic overflow 
through the neck so that often the valve does not have to 
be used at all until a landing is to be made. It is mainly 
this alternate loss of gas and ballast which finally terminates 
a balloon flight; and the principal cause of this sacrifice is 
the heating of the gas and air by the sun's rays. 

When the sunlight passes through any surface, a certain 
amount of radiant energy is transformed into heat and in 
the case of a balloon is imprisoned within, where it acts to 
raise the temperature of the gas. When the temperature 
reaches a certain point, enough heat is lost by outward 
conduction through the fabric to balance that received by 
radiation, and the temperature has then reached a maxi- 
mum. This temperature is sometimes found in a varnished 
balloon to be as much as 90° F. higher than the outside air. 

The temperature itself does not cause much trouble, but 
change in temperature does, and this is always occurring 
throughout the day, even in cloudy weather, from the con- 
stantly varying radiation from the sun. An increase in 
the temperature of course causes the gas to expand, which 

286 



BALLOONING 287 

drives out the air or gas which happens to be at the bottom 
of the balloon. Whether it is air or gas the loss of weight 
is like the loss of so much ballast and causes the balloon 
to rise. The rise is much more marked if there is air in 
the bottom of the balloon, and in this case it usually per- 
sists until all the air has been forced out. This is bound 
to occur sooner or later, however, so that a rising impulse 
always automatically checks itself in time. 

Not so with a cooling or descending impulse, however. 
There is no limit to the amount of air that can be sucked 
in so that even a slight descending impulse may often carry 
a balloon clear to the ground if ballast is not thrown out 
to stop it. Atmospheric conditions may be generally found, 
however, at certain heights where the equilibrium of the 
balloon is essentially stable in both directions. This occurs 
when the temperature gradient of the air in a downward 
direction is less than that which would result from the 
adiabatic contraction of a descending particle. 

It is the aim of a skillful balloonist to find these con- 
ditions and take advantage of them, and also to find wind 
currents which take him where he wants to go; in other 
words, he must use his ballast and gas in the best possible 
way, everything considered. 

The pilot has at his service various instruments which 
are a great aid in attaining these ends. The recording 
barograph makes a record of the height above starting 
point, on a piece of paper. The altimeter or aneroid baro- 
graph gives the altitude above the starting point at time 
of reading. The statoscope tells whether he is going up 
or down relative to the ground. The compass tells the 
direction of flight. 



288 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

INSTRUCTION DURING FLIGHT 

In case of long nights, start the log sheet as soon as the 
get-away has been made, and keep a careful record of the 
flight. The speed and the course will be variable at first, 
so should be checked up every ten or fifteen minutes. A 
good set of maps of the country should be obtained showing 
the position of railroads, bridges, towns, and other prom- 
inent points. The Rand-McNally state maps are satis- 
factory unless more reliable maps can be obtained. Keep 
a careful check on the position at all times. A megaphone 
is of assistance in obtaining information from natives below. 

Keep a watch on the air currents; this may be done by 
watching the clouds, by the smoke from the ground, by 
dropping sounding paper, but do not valve or throw sand 
any more than necessary at first, especially if out for an 
over-night or long flight, for these are the only means of 
staying aloft and may be of great value in selecting a landing 
or rather avoiding an unfavorable landing. A slow rise 
or fall may soon stop of its own accord and thereby save 
you ballast. A knowledge of the cause of these changes in 
altitude will be of assistance, such as a local change in 
temperature, a temporary increase in humidity, sun going 
behind a cloud, sun set or sun rise, vertical air currents, etc. 

A study of the daily weather charts is most useful in 
making good a certain course. Surface breezes due to local 
causes, such as land and sea breezes, may be from quite a 
different direction than that due to the prevailing low or 
high, but such breezes usually do not extend more than 
2000 feet up. You will find it a great saving in ballast to 
remain in the stable portion of an air current even if you 
have to sacrifice some speed. After nightfall and the 
temperature of the balloon has had time to adjust itself, 
you will find the atmosphere very stable and no ballast 
may be expended for a period of an hour or more. 



BALLOONING 289 

In making a long flight balloon telegrams should be dropped 
at intervals with instructions on the envelope to be de- 
livered as soon as possible to nearest telegraph office. These 
telegrams are to be sent collect to the commandant of the 
Aeronautic Station. State time of day, course and speed, 
and probable time of landing. 

In making short flights from the Station for instruction, 
no record need be kept of course, speed, etc. These flights 
are made chiefly for instruction in get-away and landings, 
and method of changing altitudes. Notes should be kept, 
however, of data showing the relation of cups or pounds of 
ballast and valving in seconds to changes in altitude and 
amount of ballast, or seconds of valving to counteract a 
rise or fall of different speeds. 

FORMULAE AND CONSTANTS FOR READY REFERENCE FOR 
19,000 CUBIC FEET FREE BALLOON 

1. Before the ascent 

(Based on normal conditions, 30 inches barometric pres- 
sure at sea level, hydrogen gas 99 per cent pure, balloon 
filled to top of appendix, temperature 70° F. unless otherwise 
stated.) 

Net lift, 900 pounds (including everything glass in the 
list of equipment) for 70°F. on a cloudy day. 

Add 23 pounds for every 10° decrease in air temperature 
and from 10 to 30 pounds for varying intensities of sunlight 
(the greatest figure being for the brightest sunlight.) 

Subtract 23 pounds for every 10° increase in the air 
temperature, and 5 to 15 pounds for varying clearness at 
night (the latter figure being for an absolutely clear day). 

Resistance of balloon before start (pounds) M-1.5 v 2 
where v is the wind velocity in miles per hour. 



290 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

V 2 

Minimum starting ballast (bags) = — tan 2 x where x is 

the angle that the balloon has to clear and v is the wind 
velocity measured from the top of the obstacle. 

2. During flight 

(Based on an average altitude of 5000 feet, otherwise 
same as previous section). 

Holding valve open 10 seconds to lose gas equivalent to 

1 bag of ballast (30 pounds). 

V 2 y 
Unbalanced force (bags) = -rr- where Vy is the vertical 

ou 

speed in feet per second. 

Drag rope 50 pounds, 220 feet long, will stop force of 
descent of 0.7 bag (6 feet per second) without hitting 60 
feet trees. 

When sun goes behind a cloud start throwing ballast at 
rate of one-third cup per minute to stay in equilibrium. 
Usual total about 1 bag. Allow at least 2 bags for transi- 
tion from daylight to dark (clear sky). Increase of weight 
in a rain may be as much as 5 bags. 

3. During flight 



Speed (miles per hour) = — where t is the time in seconds 



22 

where t is the time in secon 

H 

for the balloon to pass over a given point. Or: speed = — 

where H is the height above the ground in feet and this 
the time for an object to go through an angle of 20° from 
vertical. 

Sound travels 1100 feet per second (for check on altitude 
by echo). 



BALLOONING 291 



or 



Save at least 2| bags for landing from 10,000 feet 
over (see special landing instructions). 

List of equipment for 19000 cubic foot free balloon 

I. Dead weight 425 pounds consisting of 

Gas bag 234 

Net 42 

Suspension ring 10 

Basket 127 

Valve 1 

Valve top] 

Valve cordl 

Rip cord J 

425 

to which should be added: 

II. Instruments pounds, consisting of 

Ballast cup (to hold 3 pounds of sand) 
Barograph 
Statoscope 
Compass 
Speed indicator 
Stop watch 
Pencils 

Electric flashlight 
Knife 

And for very precise work, an asperating thermometer. 
III. Emergency ballast : 

Drag rope 45| 

Gas bag packing cloth 8 

Valve case 1 

Basket cover 5 

Basket rug 

Empty sand bags 20 

IV. Ground Equipment: 
Ground cloth 
Eighty sand bags 
Inflation tube 
Inflation sleeve 



292 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



to which should be added: 

Holding rope (about 20ft. of any strong rope) 

Supply of sand 

Repair material 

Soap for valve. 
V. Equipment for special occasions: 

Life preservers 

Pontoons 

Water anchor 

Ground anchor 

Long paper tape for soundings 

Smoked glasses for use above clouds 

Megaphone 

Binoculars 

Electric torch or lantern 

Camera- maps, camp chairs, blankets, provisions, etc. 

Table of Ballast Weights 
1 pound = 1 cup. 
35 cups = 1 bag, 30 pounds. 
5 bags = 1 person, 150 pounds. 



ANGLE 


SINE 


TANGENT 


5 


0.0872 


0.0875 


10 


0.1736 


0.1763 


15 


0.259 


0.268 


20 


0.342 


0.364 


25 


0.423 


0.466 


30 


0.500 


0.577 


35 


0.574 


0.700 


40 


0.643 


0.839 


45 


0.707 


1.000 



1.61 km. = 1 mile. 
3.20 feet = 1 m. 
2.20 pounds = 1 kgm. 
1.8° F. = 1°C. 



Table height for a 19,000 cubic foot balloon will rise for 
a given amount of ballast discharged. 



BALLOONING 
/ 



293 



Z = A 



F 



Z = height in feet. 

A = height of a homogeneous atmosphere = 26,217 

feet. 
/ = ballast in pounds thrown over. 
Fq = total ascensional force of balloon = 1330 pounds. 



BALLAST DTSCHARGED 


HEIGHT IN FEET OF ZONE OF EQUILIBRIUM 


10 


201 


20 


402 


30 


598 


60 


1210 


90 


1817 


120 


2600 


150 


3333 


180 


4104 


210 


4916 


240 


5772 


270 


5583 



INSTRUCTIONS FOR LANDING 

Just previous to landing bring the balloon down as low 
as possible without touching the drag rope. Secure the 
instruments in their cases. Instruct the passengers as to how 
to handle themselves while landing. The drag rope side 
of the basket becomes the rear of the basket after the drag 
rope touches and the top of basket when landing is made. 
By holding to the ropes on the rear side and bending the 
knees and standing on toes the shock of a hard landing may 
be avoided. No one must leave the basket until told by the 
pilot. Let the passengers know when the rip cord is pulled as 
i t gives them a second or more in which to drop what they are 



294 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

doing and to prepare for a possible shock. So far as hand- 
ling ballast, valving, etc., is concerned, the flight is over as 
soon as the rip cord is pulled. Avoid drag-roping if possible, 
but do not let the rope get more than 100 feet above the ground. 
Take into account the relative direction of the lower currents 
where difference can be noted. After the drag rope has 
touched, disregard statoscope and watch ground. When 
you want to make the final descent do not be afraid to valve 
strongly from this point. Remember that it takes ten 
seconds to let out the equivalent of one bag of ballast and 
ten seconds seems a long time when hanging on the valve. 
It takes about fifteen seconds' valving to overcome the 
weight of the drag rope. It is better to land with a good 
sharp bump than to drag. If there is a strong wind, drop 
the valve cord and pull the rip cord at least twenty feet 
in the air. The utmost care should be taken to keep this 
point in mind as the time when it is most needed is when you 
are most liable to forget it in the press of other circum- 
stances. Under usual conditions select one passenger to 
pull the rip cord and another to be ready with dispensable 
baggage. 

The landing usually collects a large crowd and it is fre- 
quently possible to let the drag rope drag on the ground 
until two or three men can get hold of it and pull the balloon 
over to a convenient landing place nearer the road. In 
making a landing you will find it of advantage to consider 
the possibilities of getting back home; so landing near a 
road or railroad station may save you twelve hours. 

Landing with the use of an anchor is of great assistance 
where the possible landing place is small in area. Have the 
anchor ready with the line hanging out of the basket, clear 
for running. Calculate the length of the anchor line 
allowed; additional distance for possible dragging before get- 
ting a good hold, and let go anchor when this distance 



BALLOONING 295 

from the desired landing place. As soon as anchor is let 
go, swing on to the valve cord and keep valve open until 
ready to rip. The anchor is very useful when making a 
stop landing, also when making a landing from over the 
bay onto the beach. 

INSTRUCTIONS FOR NIGHT FLIGHT 

Making a balloon flight at night appears to be a danger- 
ous thing to undertake to the beginner, but in reality there 
is no added danger, providing the pilot keeps track of his 
position and does not have to land on account of weather 
conditions. On the contrary, the balloon sails along in a 
very stable atmosphere, and requires very little attention 
so far as ballast is concerned. The sun going down will 
cost two or more bags of ballast, and then one or more 
bags will be expended until the temperature of the balloon 
has adjusted itself, but after that a few cups now and then 
will be sufficient to keep the altitude. The altitude to 
maintain depends on the nature of the country. With 
fairly level country, it is best to keep an altitude between 
1000 and 2000 feet. At this altitude one can hear the 
noises on the ground, such as chickens, dogs, trains and the 
wind in the trees, which will act as a check on the altitude, 
and can see the numerous lights, and on clear nights rail- 
roads, streams, roads, by means of which course and speed 
can be obtained and position located on the chart. 

It is best not to get above the clouds at night, but if you 
do, do not remain above more than one or two hours, 
especially when near water, as one loses all knowledge of 
speed or course when out of sight of ground. All clouds 
look bad at night, but a rain cloud can usually be recog- 
nized and it is best to make a landing before the increased 
wind strikes you. Thin dew clouds may be seen below 



296 



AIRPLANE'S, AIRSHIPS, AIRCRAFT ENGINES 



A &1\S> VALVE & COVfR 
S HIP PAH EL. 

c Rip cow 

O VALVE CORD 

£ RlP CORD CmIAHD 

F" APreNOlX 

Gk APPEH Ol X &RIQLE 

H BRiouC Rope 
J crow's root. 
K NET 

L Load Ri no> 

M S/JS K ET 
/N FOOT ROPES 




THE SPHERICAL FREE 
BALLOON 



HALF Op BALLOON SHOWN | IN SECTION. 
Fig. 24 



BALLOONING 297 

you during the night. These should not trouble you, as 
there are many pockets through which the ground is seen. 
In the early morning dew settles on the bag in sufficient 
quantity to drop down into the basket, and cost a bag or 
more ballast. It is wise to take along rain clothes even on 
a clear night on account of this dew. During the early 
part of the night the temperature between 1000 to 2000 
feet is frequently warmer than that near the earth, but 
after midnight the temperature begins to fall and heavier 
clothing is needed. 

If forced to land at night, drop rope over the tops of the 
trees until an open space is found. Even on the darkest 
nights the ground can be seen from the heights of the trees, 
and there is no danger if you do touch an occasional tree. 

At sunrise the balloon will begin to ascend, due to heating 
of the gases and drying out of the balloon. Unless you 
wish to make a landing soon after sunrise, it is best to let 
the balloon ascend, as the altitude will not be increased 
more than 1000 to 2000 feet. 

See figure 24 of inflated balloon for names of various 
parts, etc. 



CHAPTER XLIII 

Dilatable ob Expanding Gore Balloons 

Dilatable or expanding gore balloons have recently come 
into use in this country. They are at present used for 
aerographical research work and are similar in appearance 
to the late type kite balloons. They are much smaller, 
however, in that the Navy type under normal conditions 
upon the ground has 5000 cubic feet capacity with 0.35 
inches of water pressure. Placed on each side of this 
type of balloon and running in a longitudinal direction in 
the lower half of same is one gore in a semi-collapsed con- 
dition. This condition is brought about by the means 
of yq inch square elastic cords being attached to the rein- 
forced edges of the gores above and below the collapsed 
gores on each side. This balloon when sent aloft with aero- 
logical instruments, the gas begins to expand, but instead 
of the gas escaping through an automatic valve or an 
appendix it expands the gores previously mentioned, as 
the increased pressure stretches the elastic cords, thus 
increasing the capacity of the balloon from 5000 cubic 
feet capacity to 7400 cubic feet capacity under about 1J 
inches water pressure; this balloon will have a ceiling of 
4000 to 5000 feet. If, for any reason, it is desired to lift 
a greater weight than the normal condition of inflation 
will lift, the balloon can be inflated to more than its normal 
diameter on the ground, provided the altitude to which it 
is allowed to ascend is correspondingly reduced so that 
there is no danger of producing an internal gas pressure 
of more than If inches of water when the balloon ascends, 
and the gas is heated by the sun. 

298 



DILATABLE OR EXPANDING GORE BALLOONS 



299 




/7<£. ES. 







BALLOON 



"^3/)/V&. 



F/<r. Z&- 



300 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

It is to be noted that the rubber elastic cords are subject 
to rapid deterioration and should be taken up from time 
to time or renewed as necessary. See figures 25 and 26, 
showing location of expanding gores, elastic cords, etc. 



CHAPTER XLIV 

Fokmttla Aerostatics 
boyles law 

The temperature remaining constant, the volume varies 
inversely as the pressure. 

CHARLES LAW 

The pressure of gas remaining constant, the volume 
varies directly as the temperature. 

BOYLES AND CHARLES LAWS COMBINED 

Boyles law gives the relations that volume varies in- 
versely as the pressure while with. Charles law the volume 
varies directly as the absolute temperature; combining these 
relations we have: 

T 

V varies as — or PV = RT, which is the fundamental 
P 

gas formula, P being the pressure, >R the numerical constant 
for the gas in question and V the volume of a given portion 
of gas at the absolute temperature T. 

For example, a balloon has a capacity of 10,000 cubic 
feet at 70°F. and 30 inches of mercury pressure and it is 
required to determine its volume at 60°F. and 25 inches 
pressure. We have: 

V = F.fg = 10,000|f^|±^ = 11,820 cubic feet. 

If the density of gas at 70°F. and 30 inches pressure is 

301 



302 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

0.005 pound per cubic foot and its density at 60°F. and 
25 inches pressure is desired the formula would be as follows : 

7 7 PT * nnmr C^X 460.6 + 70) 

d = d Qj r?= 0.005 (30x460 , 6 + 60) = 0.00423 

If any two of the following four quantities are observed, 
the others can be computed — P V T D. If, for example, 
the pressure and temperature of dry air be observed at 
any point, its density can be computed from the formula, 
also its volume per pound weight and thence its volume 
for any weight. It is important, therefore, to be able 
to measure satisfactorily at least two of the four quantities 
in the studies of the atmosphere, the pressure and tempera- 
ture are observed by instruments too well known for repe- 
tition here. 

To determine the lift of gas by the law of Boyles and 
Charles, which is as follows: P = 30 inches. 

V = Vn^T = 460.6 + 70 = 530 
"i o 

Standard condition P and T are 30 inches barometric 
70°F. under which one cubic foot of pure hydrogen lifts 
0.07 pound. 

Law of Dulong and Petit : 

PTo 

PoT 



ck 



From the above laws there has been deduced an entirely 
different formula which by the use of constants which was 
derived from the law of averages and the above formula is 
considered and believed to be correct within 50 pounds in 
computing lift to an altitude of 10,000 feet. 
Lift in pounds = V 1.2366 P 

T 



FORMULA AEROSTATICS 303 

Lift — in pounds. 

V = volume in cubic feet. 
P = Barometer in inches. 

T = 460.6 T° in Fahrenheit, 

Lift = V 0.07 — -5— 0.00125 
1000 

Lift = lift in pounds under standard conditions. 
H = altitude in feet. 

V = volume in cubic feet. 

~ .,. . . , . 0rt _ Ballonet capacity 

Cemng of airship = 32.7 ^ — — 

volume of airship, total. 

Multiply ceiling by 1000 to have it in feet altitude. 



CHAPTER XLV 

Method of Preventing Tail Droop in Envelope 
of Airships 

In order to prevent the tail droop in envelopes of airships 
a gripe is suspended from the gutter of the roof of the 
hangar by the means of two single blocks that allow it to 
pass under the envelope aft of the fins. Sand bags are 
hung on the lower ends of the lines coming from the blocks 
so that they take up the strain whether the ship is on the 
deck or rises a little off the deck. 

A somewhat similar method has been used in which, 
instead of the gripe passing under the tail of the envelope, 
attachment was made directly to the horizontal surfaces. 
However, the method using the gripe seems to be simpler 
and more easily applicable. 

As soon as the ship is brought into the shed or hangar 
and secured, the weight of the tail should be picked up on 
the gripe and should not be removed until the ship is pre- 
pared to leave the shed. 

The above method preventing tail droop has been tried 
with noticeable success. 



304 



CHAPTER XLVI 

Airship Mooring 

There have been two systems of mooring airships in 
the open, and both systems have proven more or less satis- 
factory. In order to moor an airship a clearance of suffi- 
cient size should be selected before attempting to moor 
same in order that the ship can swing clear in any direction. 
The three wire plan after trials has proven to be most 
satisfactory for non-rigid type airships. This plan consists 
of utilizing the forward bridle with an additional length 
attached to the underside of the balloon in the rear of the 
bridle connection forming a triangle with sides -of about 
50 feet in length with weights, or sand bags, of about 125 
pounds being suspended to the after handling guys. If the 
foregoing weight is found to be insufficient, the weight may 
be increased to 150, 160 or 175 pounds as may be found 
necessary in order to keep the ship steady. 

The other method which has been tried abroad with 
more or less success consists of fitting an airship with a 
special rigid nose by which the ship may be attached to a 
mast for mooring out. 

The attachment consists of a built up wooden spar 15 
feet long which is rigged in the envelope with a steel fitting 
at the forward end, around which a sleeve at the nose of 
the envelope is tied off. The fitting terminates in a solid 
detachable end piece formed with an eye by means of 
which the ship is pinned to the mast. A wire passes through 
this end fitting and through the center of the spar to the 
after end where it is divided into four wires which are 
attached to a tubular ring 12 inches diameter. From this 

305 



306 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

ring 52 strings radiate forward in the form of a cone (whose 
base is 18 feet in diameter) to patches on the inside of the 
envelope. 

From a flange on the eye piece at the foremost end of 
the spar six wires are led back to Eta patches These 
wires form a cone which is opposed to the cone formed by 
the strings. These two cones serve to attach the spar 
(and with it the eye at the foremost end) to the envelope, 
with a fair degree of rigidity. It is easily seen that the 
spar cannot move relatively to the envelope as a whole 
unless the annulus where the strings are attached is deformed. 

The device is further intended to serve the purpose of the 
usual nose stiffener. To this end, that part of the nose 
over which the external pressure is greater than the normal 
internal pressure at full speed has been replaced by a new 
piece about 4 feet 6 inches in diameter of reversed curvature. 

The wire which passes through the center of the spar 
is brought out through a clamp in the eyepiece and a free 
length of about 70 feet is left which is used to bring the 
ship up to the mast and is intended to be attached to the 
car during flight. By loosening the clamp the wire may be 
hauled through the spar to adjust the tension of the strings 
of the rear cone, the wire being then reclamped. This can 
be done while the ship is attached to the mast. A rotating 
casting is fitted to the head of the mast designed to receive 
the wire at the head of the spar. 

The procedure when attaching the ship to the mast is as 
follows: A hemp rope is laid over the mast head in a 
forked guide and one end is then made fast to the wire from 
the ship's nose. The other end of the rope is then hauled 
through a block on the ground. 

When the wire reaches the mast head the pull is eased 
and the wire is lifted into a groove in the casting and the 
ship hauled up until the eye enters the casting. The pin 



AIRSHIP MOORING 307 

is then inserted. A stern rope is used to check the approach 
to the mast and the ordinary handling guys are, of course, 
used. 

This latter method has been used in mooring out non-rigid 
airships and while more or less satisfactory it is not con- 
sidered as satisfactory for non-rigid type airships for moor- 
ing purposes as the three wire method mentioned in the 
foregoing. However, it may be used satisfactorily for the 
smaller non-rigid type of airships, whereby the nose of the 
airship can be sufficiently reinforced to take care of the nose 
fitting and the strain can be distributed over a greater 
area; then this method will be far more satisfactory than 
the triangle bridle suspension. 

A cheaper, but tried, method of mooring rigid airships, 
more of an emergency measure, is the three wire system. 
This requires in addition to the landing ground fixed con- 
crete anchorages with some simple gear for the three moor- 
ing cables. 

The mooring mast previously referred to is constructed 
of steel and on the latticed principle. All of the details 
in connection with the best methods and principles of moor- 
ing airships are at the present period in a stage of evolu- 
tion. Therefore, only a general description of the methods 
which have been tried is given. 

The following is a general description of an airship moor- 
ing mast erected at Pulham, England: 

The mast itself is a web-steel structure 115 feet in height 
with a revolving circular platform housed-in at the top 
and above the platform a mooring apparatus in cylindrical 
form swung on gimbals which permits the ship when moored 
to sway with the wind and swing to all points of the compass. 

In addition to an elevator for passengers and freight 
purposes, the mast contains pipes for furnishing water 
ballast, gasoline, lubricating oil, and lifting gas for the 
airship. 



308 



It is said that the rigid airship, R-33, sister ship of the 
R-34, which crossed the Atlantic to the United States in 
1919, has been moored to one of these masts. She has 
ridden out gales when the wind reached a velocity of 90 
miles per hour, and she has been moored and released from 
the mast at wind speed as high as 50 miles per hour without 
damage or mishap. 

The method of mooring with this type of mast is as 
follows : 

When an airship approaches a mooring mast a cable, 
which runs from a winch from the ground up the mast and 
through the cylinder, is led down again to the ground and 
out to a point about 600 feet from the mast in the direction 
from which the airship is approaching. Two men stand 
by the end of the cable, one man at the winch, and three 
to five others in the top of the mast. They transmit signals 
and operate the cables and machinery. 

The airship approaches the end of the cable lying on the 
ground at a height of about 500 feet, her mooring being 
let down in a loop. When the loop is over the end of the 
cable stretched out on the surface, the outboard end of the 
cable is dropped to the ground. It is then shackled up to 
the mooring mast cable and at a signal from the men on 
the ground, ballast is discharged from the airship until 
she is about 2 tons light, and trimmed down at the stern. 
She then rises to a height of about 1200 feet above the 
trim. 

At a signal from the airship, "Haul down," the winch is 
started and the cable draws the airship down toward the 
head of the mast. When the airship is about 500 feet 
above the top of the mast two other cables about 600 feet 
long are let out, leading from the bow of the ship, and 
these cables are secured to two surging cables on the mast 
and the ends of the two cables are drawn up by lead lines 



AIRSHIP MOORING 309 

to the forward hatch of the ship. From then on, a strain 
is maintained on all three cables and the airship drawn 
down until a cone on her bow fits into a cone on the top 
of cylinder of the mooring mast. When the two cylinders 
are firmly "set home," locking springs lock the ship to the 
mooring mast. 

An airship moored to a mast must always be kept trimmed 
down by the stern. And this is also true when landing or 
getting away, otherwise gusts of wind downward on the 
bow of the ship would throw her stern up and cause her to 
surge about and "whip" in the air. 

To release an airship from a mooring mast, it is only 
necessary to let down a pendant from her nose throuh the 
revolving cylinder where a tension is put on it by a hand 
reel in the top of the mast, and the strain is held until the 
locking springs are free. In the meantime the after engine 
has been started to neutralize the force of the wind which 
tends to drive the airship astern. When all is reacfy, the 
remaining engines are started up, the locking springs are 
pulled back, and the ship rises free from the mast. 

These masts do away with landing dangers in inclement 
weather. They also make it easier for passengers to enter 
the ship, for, after the passengers are landed in the revolving 
platform, they merely step through an "accordion" door- 
way similar to the connection between parlor cars on a 
passenger train, and walk down the passage into the ship's 
cabins. 

As yet this type of mast has not been built in the United 
States. 



CHAPTER XL VII 
Lighter- Than- Aib — Aircraft Don't's 

a. Don't allow either engine to be run while inflating or 
deflating in a shed or hangar, or while filling gasoline tanks. 

b. Don't run gasoline through chamois unless funnel is 
grounded to can and car. 

c. Don't run the engine full power more than necessary, 
especially on the ground. 

d. Don't exhaust all the fuel from the forward or largest 
tank as this is the only one that supplies the small engine 
(blower). 

e. Don't forget the emergency tool kit (carried in airship). 
/. Don't carry more total load in the car than that in- 
dicated under useful load. Put air in the ballonet instead. 

g. Don't get the handles of the dampers on the air scoop 
on so that the dampers cannot be closed. Check this so 
that the handle will be up when the damper is closed. 

h. Don't allow men with other than rubber soled shoes 
to walk on bag, and then only when absolutely necessary. 

i. Don't allow sharp edges of fins to injure envelope. 

j. Don't allow any kinks in cables, suspension or control. 

h. Don't try to locate car by load rings. Check align- 
ment by having it in line with front nose rope and tail rope. 
Measure from top of longeron, the front end of the car 

should be feet, and the rear end feet from the 

bag. (According to blueprint.) 

Z. Don't lead the control valve cords so that they will 
get foul of the propellers. 

m. Don't have undue stress on cables. All suspension 

310 



AIRCRAFT DONVs 311 

cables should be proportionately tensioned. Use tension 
meter and apply tension as per assembly diagram. 

n. Don't have control cables to elevators and rudder set 
up too tight. There should be no sag in them with 1 
inch gas pressure in envelope. 

o. Don't forget to examine the fire extinguisher and see 
that it is properly charged and in place. 

p. Don't forget in balancing the ship with all loads in 
place that the ship should be evenly balanced (power off). 

q. Don't let the pressure go above 1.5 inches as shown by 
the manometers, or below 0.7 when under power. 

r. Don't run the engine when the bag has been allowed 
to buckle. Throttle or stop the engine altogether and 
rise slowly by use of ballast until pressure is restored. 

s. Don't use the blower during flight unless the main 
engine is out of commission. 

t. Don't discharge gas simultaneously with air unless sure 
that there is a surplus. 

u. Don't wait for the safety valve to blow if you can 
conveniently help it. 

v. Don't, under any condition, exceed 25 degrees angle 
either up or down as the suspension is not designed for more. 

w. Don't try to put the ship in the hangar with a cross 
wind of 25 miles per hour without sufficient men. As 
many as 12 men can be placed on any one of the yq inch 
cables that pull essentially tangential to the gas bag. 

x. Don't touch or come within six feet of a valve, either 
air or gas, while it is blowing, except in the following cases: 
(a) For adjustment of air valve, the air may be blown 
through for several minutes to be sure of flushing out 
accumulated hydrogen that has diffused through, after 
which the valve may be freely touched when necessary 
during the process of adjustment, (b) In the case of gas 
valves, if it is necessary to touch them while they are 



312 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

blowing, contact with the body should be made before they 
have started to blow and continue until they have stopped. 

y. Don't use anything but high test benzine, when wash- 
ing balloon fabric or diluting cement. 

z. Don't store a balloon away in a damp warm place. 
It should be stored in a dry cool dark place, as sunlight is 
injurious to rubber. 

AA. Don't fail to use a gas mask when it becomes neces- 
sary to dope the fabric on the interior of airships, otherwise 
you may be overcome by the dope fumes. 



CHAPTER XLVIII 

Things to Remember About Airships 

1. That valve and other adjustments change with time 
especially during the first few days, in a new balloon just 
rigged. 

2. To inspect the balloon systematically, always with a 
view to preventing trouble in the air. 

3. That emergency repairs may often be made in the 
air and a few simple tools should be carried for this purpose. 

4. Not to use the gas bag as a rug, or as a means of 
concealing small objects. No pins, tacks, or bottles should 
be allowed in the hangar. Put a rope rail around the bag 
to prevent walking on it. 

5. That hydrogen gas is highly inflammable, and danger- 
ously explosive when mixed with air. 

6. That one may easily without warning be overcome by 
breathing gas around valves, etc. When working on a 
tall ladder around the balloon, it is best to be tied on. 

7. Always to leave the magneto switch off and the spark 
retarded when not running the engine. 

8. To keep clear of the propeller when it is moving or 
when there is a man at the engine. 

9. That it takes careful steering to hold the nose into the 
wind after the drag rope has been caught. 

10. To have a surplus lift for landing. 

11. Not to try to land like an aeroplane. Always use 
the drag rope on land or water. 

12. That the tail swings opposite to the direction in 
which you turn. Always allow plenty of room. 

13. To watch the manometers. 

313 



314 



14. The propeller stream is what runs the ship. One 
square foot of flat surface or its equivalent behind the 
propeller cuts down the speed approximately one mile per 
hour. 

15. Not to run more than 1200 revolutions unless neces- 
sary. This will cut in half the danger of engine trouble. 

16. By sacrificing gas during flight you can do many 
tricks successfully that you pay for later at landing. 

17. All valves should be rechecked after one days flying 
and then again within four or five days when the bag is 
new. The air valves are subject to other variations and 
should be checked frequently. 

18. When adjusting gas valves be very careful about 
static. Touch hands to the bag (fabric) first before touch- 
ing the valve or any other metal part connected to the 



19. To have three or more bags of sand ballast open 
and ready to dump at a moment's notice, but so that they 
will not be dumped until required. 

20. To fly high if carrying a surplus load. 

21. To throttle engine and close air damper simultane- 
ously with the dropping of the drag rope. Be ready to 
throw out ballast again if the men fail to get the drag 
rope. 

22. To keep the nose into the wind with rudder and 
assist with engine if necessary as the balloon is pulled 
slowly to the ground. 

23. That when rear ballonet is full of air its pressure is 
0.7 inch higher than the gas, and forward ballonet is 0.5 
inch higher than the gas. 

24. And that a down tilt of more than 15 degrees reduces 
the pressure in the nose below that indicated by the gas 
manometer. 



THINGS TO REMEMBER 315 

25. Never to let the balloon stand needlessly with air in 
the ballonets. Air or gas must be put in, however, if the 
pressure gets below 0.4 inch. Maintain a gas pressure of 
about 0.5 inch as far as possible. 

26. To analyze the gas once every 24 hours, as long as 
the purity is above 90 per cent. When the air content 
becomes greater than 15 per cent deflate and refill with 
pure gas. 

27. That one J inch hole in the fabric of a gas bag will 
let out more gas than escapes by diffusion through the entire 
fabric of the balloon." 

28. To keep hangar doors open whenever possible, es- 
pecially when inflating or valve testing. 

29. To have one parachute for each man in the car before 
leaving the ground, properly secured in place and each man 
informed as to which he is to use. Harness to be worn 
at all times with parachutes ready to be hooked when leav- 
ing the ground. 

30. Never pack a parachute when it is damp, moist or 
wet. 



CHAPTER XLIX 

Aieckaft Engines 

pkeliminary units and definitions 

Q. 1. What elementary units and terms connected with 
the generation of power must be known in order that the 
study of the operation, maintenance and repair of aeronauti- 
cal engines may be understood? 

A. (1) Force; (2) work; (3) energy; (4) power; (5) horse 
power (indicated horse power and brake horse power); 
(6) friction; (7) mechanical efficiency; (8) thermal efficiency; 
(9) compression; (10) combustion; (11) torque; (12) torque 
reaction; (13) inertia. 

Q. 2. What is force? 

A. Force is that which causes acceleration or retardation 
of a body. 

Q. 3. Define work. 

A. Work is the overcoming of resistance through space. 
Work is usually expressed in terms of foot-pounds. If a 
force of 10 pounds acts through a distance of 10 feet, it 
will do 100-foot pounds of work. 

Q. 4. What is energy? 

A. Energy is the ability to do work. 

Q. 5. What is power? 

A. Power is the rate of doing work and is the amount of 
work accomplished in a given time. 

316 



AIRCRAFT ENGINES 317 

Q. 6. Define horse-power. 

A. Horse power is the practical unit of power, one horse- 
power being equal to that amount of work which is done 
when a weight of 33,000 pounds is raised one foot in one 
minute of time. The abbreviation "H. P." is used to 
denote horse-power. 

Q. 7. Define indicated horse-power. 

A. The indicated horse-power of an engine is the power 
developed in the cylinders by the pressure and expansion 
of the gas. It is determined by the formula 

pj^n. = ihp 

33,000 

P. represents M.E.P. pounds (Mean Effective Pres- 
sure) . 

L. represents the stroke in feet. 

A. represents the area of the piston head in square 
inches. 

N. represents the number of power strokes per minute. 

The pressures in the cylinder are determined by means 
of an instrument known as an "Indicator" which records 
the varying pressures during the cycle. 

Q. 8. What is brake horse-power (B.H.P.)? 

A. Brake horse-power is the actual horse-power available 
after all losses due to friction, heat, etc., have been over- 
come. Brake horse-power is usually determined by use of 
dynamometer or Prony brake, the dynamometer being the 
most suitable means. The dynamometer consists of a 
dynamo which is connected to and driven by the engine 
being tested. The amount of electricity generated by the 
dynamo is measured in terms of Watts, 746 Watts being 



318 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 






equivalent to one horse-power, and in this manner the 
number of Watts generated determine the horse-power of 
the engine. 

Q. 9. What is frictional horse-power? 

A. Frictional horse-power is the power consumed in 
overcoming the friction of the moving parts and is approx- 
imately 5 per cent of the power developed. 

Q. 10. Define mechanical efficiency. 

A. Mechanical efficiency is the percent of efficiency ob- 
tained from an engine in the mechanical sense. The pro- 
portion found by dividing the B.H.P. by the I.H.P., ex- 
pressed as percentage, would be the mechanical efficiency. 

Q. 11. What is meant by the term " thermal efficiency?" 
A. Thermal efficiency is the ratio of the energy given 
out at the crankshaft and the energy supplied in the form 
of fuel. Each pound of fuel supplied contains a certain 
amount of inherent energy, this energy being expressed as 
British Thermal Units, each B.T.U. containing the equiva- 
lent of 778 foot-pounds work. By comparing the weight 
of the fuel consumed over a given time to the amount of 
energy received from the engine during the same time, and 
subtracting the frictional losses, is found the thermal effi- 
ciency of the engine, which is expressed in terms of 
percentage. 

Q. 12. What is meant by the term " compression?" 
A. Compression is the act performed by the piston of 
causing the gas in the cylinder to occupy a smaller space. 
In an aeronautical engine, compression is performed by the 
piston on what is known as the compression stroke. The 
charge having been drawn into the cylinder, the piston is 



AIRCRAFT ENGINES 319 

at the bottom center; all valves are then closed. The pis- 
ton during the up-stroke (compression stroke), compresses 
the gas, confining it at the end of the compression stroke 
in the combustion chamber at high pressure. By compress- 
ing the gas its temperature is raised nearer to its ignition 
point and it is more easily ignited and gives off more ex- 
plosive power than if at atmospheric pressure. 

Q. 13. What is combustion? 

A. Combustion is the burning of the compressed charge 
in the combustion chamber and is usually referred to as 
as explosion. 

Q. 14." What is torque? 

A. Torque is the twisting motion applied to the crank- 
shaft by the reciprocating motion of the pistons which is 
transmitted to the crankshaft by the connecting rod and 
crank. 

Q. 15. What is torque re-action? 

A. Torque re-action is the re-action applied to the sta- 
tionary parts of the engine by the torque and is of course 
in an opposite direction to the direction of rotation of the 
crank-shaft. Torque re-action is the tendency of the 
stationary parts of the engine, such as crankcase, cylinders, 
etc., to rotate in an opposite direction to that of the crank- 
shaft. 

Q. 16. What is inertia? 

A. Inertia is the tendency of a body at rest to remain 
at rest, or of a body in motion to continue in motion, until 
acted upon by some outside force. 



320 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

AIRCRAFT ENGINES 

Q. 1. What is an internal combustion engine? 

A. An internal combustion engine is a machine which 
converts the heat energy in a volatile fuel (gasoline) into 
mechanical energy. 

Q. 2. Give a brief description of an internal combustion 
engine? 

A. An internal combustion engine consists of one or 
more cylinders into which a charge of gasoline vapor and 
air is drawn, compressed into a combustion chamber and 
exploded. The force of the explosion and rapid expansion 
of the charge forces a piston downward within this cylinder. 
This reciprocating motion is converted to a rotary motion 
through the medium of a connecting rod and crankshaft. 
A carburetor is used for mixing this gasoline vapor and air 
in the proper proportions, and is connected to the cylinder 
with a pipe known as the intake manifold. Some electrical 
device must be used to ignite or light the charge at the 
right time, and this electrical device may be either a magneto 
or a battery generator combination. The admission of this 
charge into the cylinder must occur at the proper time, 
so it is controlled by an intake valve. After it is burned 
it must be expelled to the atmosphere at the right moment, 
and this is controlled by an exhaust valve. A crank case 
encloses the crankshaft, and also serves as a receptacle for 
the oil, as well as holding the bearings. 

Q. 3. Into what two general classes are internal combus- 
tion engines divided? 

A. Internal combustion engines are divided into two 
separate classes: (1) Two stroke cycle, (2) four stroke cycle. 



AIRCRAFT ENGINES 321 

Q. 4. Explain the operation of a two stroke cycle engine? 

A . In the two stroke cycle engine the mixture of gasoline 
and air is drawn into the cylinders exploded and forced out in 
one complete revolution, giving us a power stroke every 
revolution. 

Q. 5. Explain the operation of a four stroke cycle engine? 

A. In a four stroke cycle engine we have a power stroke 
every 4 cycles (or movements of the piston from lower 
dead center toward upper dead center), which gives a 
power stroke every two revolutions, for two movements or 
cycles occur every one revolution (once from upper dead 
center downward and once from lower dead center upward), 
In defining each cycle of operation in its turn we start 
with: 

1. Suction. During this cycle or movement of the piston 
downward, a vacuum draws into the cylinder a mixture of 
gasoline and air in proper proportions, which later on is 
to be used to give us our power. During this time the 
intake or inlet valve is held open. 

2. Compression. During this cycle or movement of the 
piston upward, the intake or inlet valve closes, so this 
charge of gasoline and air is compressed within the com- 
bustion chamber. While doing this we cause this charge 
to become so hot that it is almost to the point of exploding. 
By compressing the charge we also increase its explosive 
energy. 

3. Combustion. During this cycle of operation we ignite 
the compressed charge, exploding it, thereby forcing the 
piston downward. This cycle is the one that gives us our 
power, and it is stored in a fly wheel, or in the case of an 
aircraft engine, in the propeller. This portion of the energy 
so stored enables the engine to run over the three cycles 



322 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

that do not give back power, namely, suction, compression 
and exhaust. 

4. Exhaust. When the piston reaches bottom dead center 
the exhaust valve opens, and as the piston starts moving 
toward upper dead center it creates a pressure within the 
cylinder which forces the burned gases out into the atmos- 
phere, so we are now ready to start over again on number 
one or the suction stroke. 

Q. 6. What is an aircraft engine? 

A. An aircraft engine is an internal combustion engine, 
more refined in design and construction than either the 
stationary, marine or automobile type engine, and which is 
especially adapted for use in all types of aircraft. It is 
designed with the view of obtaining the maximum power from 
a minimum amount of weight and a low fuel consumption. 

Q. 7. Into what classes would you divide aircraft engines? 
A. There are two distinctly different types of aircraft 
engines. 

1. The fixed or reciprocating type. 

2. The rotary or revolving type. 

The fixed type in turn is divided into several classes. 

1. Cylinders all in line, upright, as in the case of the four 
and six cylinder engine. 

2. Cylinders opposed and horizontal, ,as in the case of a 
very few two, four, six, eight and twelve cylinder engines. 

3. Cylinders set V shape at an angle of 45 to 60 or 90 
degrees, as in the case of most eight and twelve cylinder 
engines. As a general rule all eight cylinder engines are set 
with the cylinder banks 90 degrees apart. This is done to 
make the power impulses even, or in other words, to occur 
every 90 degrees. In the case of twelve cylinder engines, the 
cylinder banks should be spaced at an angle of 60 degrees to 



AIRCRAFT ENGINES 323 

insure an equal flow of power, but some engineers have 
spaced their cylinders 45 degrees in order to decrease the 
amount of head resistance, and at the same time eliminate 
friction (or at least reduce it to a minimum). When the 
cylinder banks of a twelve cylinder engine are set at an angle 
of 45 degrees, the power impulses do not occur evenly, but 
45 degrees and 75 degrees apart, however it is assumed that 
the gain by reducing heat resistance and friction more than 
compensates for the unequal application of the power 
impulses. 

4. Cylinders spaced equally in a circle as in the radial 
type of engine. 

5. In the rotary or revolving type of aircraft engine, the 
cylinders are spaced equally apart in a circle, and the crank- 
shaft is held stationary, allowing the cylinders and crank- 
case to revolve, just opposite to the fixed type of aircraft 
engine where the cylinders and crankcase are stationary and 
the crankshaft revolving. Both the fixed and rotary types 
have advantages and disadvantages which we shall discuss 
later. 

Q. 8. What advantages has the fixed or reciprocating type 
of aircraft engine over the rotary or revolving type? 

A. Although as a general rule all fixed types of aircraft en- 
gines are somewhat heavier than the rotary type, for they gen- 
erally weigh from 3 to 4 pounds per B.H.P. against the 2 to 3 
pounds per B.H.P. for the rotary type, the per cent of thermal 
efficiency is very much higher in the fixed type of aircraft 
engine. Therefore the fuel consumption is correspondingly 
lower. With this in mind we should then select a rotary 
motor for high speed aircraft that are to fly only short trips, 
for that would reduce the amount and also the weight of the 
gasoline that would have to be carried. The fixed type 
should be used for low speed long trip machines, as the low 



324 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

fuel consumption also reduces the weight of the fuel, as we 
would not have to carry as large an amount as necessary 
for the rotary type flying an equal distance. Then, too, the 
fixed type is more reliable than the rotary for several reasons. 
As a rule they are water cooled, which is about 20 per cent 
more efficient than air cooling. We can secure a greater 
number of flying hours between overhauls with the fixed 
type, for in the rotary type the centrifugal force throws the 
oil out into the hot combustion chamber where it carbonizes, 
and this carbon deposit must be removed very often in order 
to secure satisfactory operation. 

Q. 9. Explain briefly the operation of the rotary engine? 

A. Of this type the " Gnome" is the best known, and in 
describing the operation of the rotary engine, the 100 H.P. 
"Gnome Monosoupape" engine will be used. 

In describing the Gnome, the word Monosoupape means 
1 valve or single valve. In the very early type of Gnome, 
there were two valves, one in the piston head and one in the 
cylinder head. However, the valve in the piston head was 
very hard to adjust, and sometimes if it didn't seat exactly 
right, fire and even explosions would occur. The modern 
Gnome engine has a single valve to allow the exhaust gases 
to leave, and by passes the mixture from the crankcase in a 
way very similar to that used in two cycle engines. The 
hollow crankshaft serves the purpose of a gasoline and oil 
pipe. Gasoline is forced through this shaft under a pressure 
of 5 pounds per square inch, and therefore we have a very 
rich mixture in the crankcase. The exhaust valve remains 
open long after the burned gases are expelled from the 
cylinder, which allows a charge of fresh air to be drawn in. 
By drawing in this fresh air charge, we dilute this very rich 
mixture to the proper proportion, and at the same time cool 
the cylinder to some extent. It must be remembered that 



AIRCKAFT ENGINES 325 

castor oil must be used in all rotary engines, for a mineral 
oil would be destroyed by the action of the gasoline in the 
crankcase. It is not necessary to go further into details on 
rotary engines, for the fixed or reciprocating type is more 
commonly used, and from all indications will replace the 
rotary altogether. 

Q. 10. What special makes of aircraft engines are used by 
the navy, and how are they classified? 

A. The navy uses the Hispano-Suiza type "A" (150 
H.P.) engine in the N-9 seaplane for elementary training, the 
Navy Liberty engine for the heavy flying boats, and the 
Union Aircraft engine for lighter than air work on airships. 
All these engines are of the fixed or reciprocating type of, four 
stroke cycles. As all these engines operate on exactly the 
same principle, a detail study of the fixed or reciprocating 
type of engine will be made. 

Q. 11. How would you determine whether or not a 
certain make of engine is suitable for aircraft work? 

A . Three items must be considered to determine whether 
or not an engine is suitable for aircraft work. They are: 

1. Unit weight per horse power. 

2. Reliability, or its ability to run for a predetermined 
length of time. 

3. Adaptability, meaning features and attachments of the 
engine which affect reliability. 

Q. 12. How would you analyze the weight factor? 

A. Weight must include all attached or detached acces- 
sories, such as radiator, fuel and oil tanks, water piping, fuel 
piping, instruments and connections. The supply weight, 
which is fuel, oil and water carried in flight, must be included, 
with reference to time of contemplated flight. When we 



326 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

speak of the weight of an engine, we always refer to the power 
delivered; for instance, we say an engine always weighs so 
many pounds per brake horsepower. If the engine is any 
way near right the water will not be consumed to an appre- 
ciable extent, but oil and gasoline are consumed so fast that 
it makes a big difference as to how much is to be carried. It 
is understood that the enlisted personnel concerned with the 
operation of aircraft engines will never be called upon to 
decide which engine is best and how fuel consumption affects 
the weight of the load to be carried. But proper adjustment 
of the carburetor will make a vast difference in fuel con- 
sumption so it always should be done very accurately. 

Q. 13. How would you determine whether or not an engine 
is reliable, and how could you aid in obtaining reliability? 

A. In view of the fact that there is never absolute reliabil- 
ity in aircraft engines, we are forced to a comparison. Some 
engines are more reliable than others, and then, too, some 
mechanics are able to secure more flying time than others. 
Reliability is best measured by how many hours it will take 
before a drop in power and speed is noticed, or how many 
hours pass before a complete stoppage occurs. The Navy 
Department desires an engine to fly for seventy-five hours 
before it is overhauled, and this is easily done, providing the 
man on the beach directly concerned with the operation 
does his work well. Therefore, remember that no matter 
how carefully an engine is overhauled in the shop, it will not 
fly the required time unless the mechanician in charge 
handles it as any very delicate piece of machinery should be, 
and that is with great care. The mechanician should take 
great pride in having his engine turn up to a little above its 
rated speed; he should also notice every adjustment and see 
that "she" is running right up to "snuff." 



AIRCRAFT ENGINES 327 

Q. 14. What are the general causes of loss of power, 
breakage and stoppage? 

A. The first and most important cause is power process 
derangements, and are those which include all operations con- 
cerned with power and fuel and not metal. These are not 
easily found, and are more continually present. The second 
is metal derangements, which always announce themselves 
soon, as a piston slap, loose bearings or gears and broken 
parts. 

Q. 15. Give a complete definition of power processes? 
A. The three power processes are: 

1. The making of a suitable mixture and its introduction 
into the cylinder. 

2. Involving the proper cylinder treatment of the working 
charge. 

3. Adequate internal temperature control of the combus- 
tion chamber. 

Even if all metal parts are correct, the engine will not run 
successfully unless the power processes are not concerned 
with the power given and the fuel consumption. 

Q. 16. Analyze carefully the first power process mixture 
making; what should constitute a good mixture, and what 
harmful effects are caused by an improper mixture? 

A. A mixture is said to be correct when it is correct in 
quality and quantity, or in other words, when the cylinder 
receives the maximum amount of the best kind of a mixture. 

Judging quality. There is a natural tendency for gas and 
air to laminate instead of mixing. We mean by that, that 
the gas and air tend to form one against the other in layers 
instead of mixing thoroughly. Therefore, when we force the 
correct proportions of gas and air into a complete mixture, 
it is said to be of proper quality. 



328 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Proportion. The proportion that is correct is that which 
leaves no gas unburned or air unused; the exhaust should 
show no unburned gas or free oxygen. The correct propor- 
tion is 15 or 16 pounds air to 1 pound of gas, and if this is 
not reached air mixture is over rich or over lean. If our 
mixture is only slightly rich, we will gain a little more power 
when running fast, for combustion occurs faster, but this is 
not an advantage for when this excess of fuel comes into 
contact with the hot flame during combustion, it separates 
into hydrogen and carbon. When this carbon in turn comes 
into contact with the colder surface of the piston, it sticks 
there building up a deposit of carbon. Later on this carbon 
becomes incandescent or red hot and ignites the mixture 
before the proper time causing preignition, which in turn 
causes the engine to knock. It must be remembered that if 
we have an excess of 10 per cent gas, or a rich mixture, it is 
the same as wasting 10 per cent from the tank, and if there 
is a great excess of gas, there will not only be a great waste, 
but combustion will occur slower, causing a loss in power, 
and a gain of carbon. If our mixture is only slightly lean, 
the speed of combustion will be impaired, causing a loss of 
speed, power, and efficiency. If there is still a greater excess 
of air, we will backfire into the carburetor, which is extremely 
dangerous in aircraft work. It must be also remembered 
that carbon is an excellent non-conductor of heat, and this 
is a serious matter in aircraft engines, for they run hot at 
all times. The manifold should be smooth so as to offer the 
least resistance to the flow of gas. Any mixture of gases 
will weigh most when their pressure is highest and their 
temperature lowest; therefore, the charge must be kept as 
cool as possible and its pressure as high as possible, until the 
inlet valve closes. 



AIRCRAFT ENGINES 329 

Q. 17. Analyze carefully the second power process, involv- 
ing the proper cylinder treatment of the working charge: 
ignition and combustion? 

A. Before studying ignition and combustion, it must be 
noted that unless our cylinder is perfectly air tight, the com- 
pression cannot be very high. Therefore, valves must be 
ground very carefully in order that they will seat properly, 
and the valves and seats both must be examined for distor- 
tions or warpage, as it is impossible to secure a good fit unless 
the material fits squarely. The cylinder also should be tested 
for leaks. A good way is to fill it with illuminating gas and 
then run a light taper around the outside. When a flash is 
noted there will be a leak. Leaks can occur past the piston, 
so great care should be exercised in fitting the rings on the 
piston and the piston in the cylinder. 

Combustion. Combustion should start, so that it will be 
completed when the piston passes over upper dead center. 
Instantaneous combustion is impossible; therefore, it must 
last over a certain length of time, and a certain number of 
degrees of crank travel, so for example, we will say combus- 
tion starts very soon after the piston passes upper dead 
center and lasts through a travel of from 10 to 20 degrees. The 
quicker the mixture burns the better, so we see that the 
ignition factor is of great importance. 

Ignition. Ignition is means whereby the charge is ignited 
or lit by an electric arc within the combustion chamber. 
Great care must be exercised in adjusting ignition equip- 
ment, for in order that combustion will be caused to occur 
at the proper time, ignition must be timed correctly. 

Q. 18. What are the essential elements of any electrical 
ignition system? 
A . They are : 
1. A simple and practical method of current production. 



330 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

2. A suitable timing apparatus which should cause the 
spark to occur at the right time during the cycles of operation. 

3. Suitable wiring to convey the current produced from 
either the generator or magneto to the spark plug within the 
combustion chamber. 

4. A spark plug built to withstand the intense heat gen- 
erated in the chamber. 

Q. 19. Which of the two (single or double) ignition systems 
is best and why? 

A. In aircraft work the double system is best for two 
reasons : 

1. It increases speed and power. 

2. Both systems seldom become inoperative at the same 
time, therefore, we are always sure of having at least one 
unit functioning properly. 

Q. 20. Explain in detail the speed and power increase 
derived by the use of two spark plugs? 

A. In our study of combustion, we have seen that the 
quicker our mixture burns, the faster our engine will run; 
then, too, power increases to a certain extent .as speed 
increases. The compressed charge in the combustion cham- 
ber does not ignite all at once, but burns in spherical form 
radiating outward. In other words, the amount of gas 
nearest the spark plug will ignite first and spread outward 
somewhat similar to the action of water in a pool if one were 
to throw a stone in the center of it. First one would see a 
circle form where the stone hit the water, this circle in turn 
inducing other larger circles to form until the entire surface 
is agitated. Under ordinary conditions, that is to say in 
automobile or marine types of engines, single ignition will 
cause combustion to occur fast enough. In aircraft engines 
however we arrange a spark plug at either side of the com- 



AIRCEAFT ENGINES 331 

bustion chamber and ignite the charge in two different 
places causing combustion to occur almost twice as quick. 
It is well to remember that unless the two plugs fire at 
exactly the same time, one plug is useless; therefore, great 
care should be exercised in synchronizing the ignition units; 
or in other words, great care should be used in adjusting 
these units in order that they may fire together. 

Q. 21. What methods of electrical current production are 
used in aircraft engines ; which is best and why? 

A. The magneto and battery generator systems are both 
used, and engineers disagree as to which is best. The 
magneto is more compact, as it generates high tension current 
within itself; however, with the exception of the "Dixie," 
they do not generate a heavy voltage at low speeds, and most 
generally a too heavy voltage at high speeds. As a general 
rule, it is easier to maintain a magneto in working condition, 
than it is a battery generator. Both of these systems will 
be studied in detail later on. 

Q. 22. Analyze carefully the third power process involving 
internal temperature control? 

A. Assuming that we have an excellent charge, and good 
working conditions, our motor would stop providing that the 
internal temperature, or the heat within the cylinder, was 
not controlled; therefore, adequate internal temperature con- 
trol is absolutely necessary to insure the proper operation of 
an aircraft engine. An explosion that will generate the power 
derived from aircraft engines generates a great amount of 
heat, and this heat must be carried by the heat conducting 
parts to the water circulating through the jacket and radia- 
tor. The design and construction of the piston is an impor- 
tant matter, for it controls the heat in the cylinder to some 



332 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

extent. An aluminum piston tapering from the center of the 
head outward and from the top downward should take the heat 
to the cylinder walls and thence to the circulating water, for 
aluminum is a very good conductor of heat. However, 
aluminum expands more than steel, or cast iron so greater 
clearance must be allowed. It must be remembered that no 
matter how carefully a piston is designed and constructed, it 
will not function properly as a heat conductor unless the mech- 
anician uses the greatest care fitting it into the cylinder. 
The oil used in lubricating the cylinder walls is also used as 
a thermal bridge or heat path; therefore, the mechanic 
should at all times check his lubrication system in order that 
this thermal bridge may be maintained. 

Q. 23. What two common adjustments are most impor- 
tant as to their effects on power processes? 

A. The closing of the inlet or intake valve must be most 
accurately timed in order to insure the pressure resulting 
from high velocity to take place within the cylinder instead 
of in the manifold; this is more essential on aviation engines, 
in fact it is the most important adjustment on the engine. 

The opening of the exhaust valve is next in importance. 
If this valve opens too soon we will lose power; if it opens too 
late we will not be allowed to empty our cylinder of all the 
burned gases. 

Q. 24. Why is aircraft engine construction important, and 
how does it effect operation? 

A. Unit weight per horsepower and reliability are depend- 
ent upon the proper construction or the arranging or forming 
of all parts, bearing in mind the function of the part and its 
relation to other parts. A general knowledge of construc- 
tion, on the part of the mechanic, will insure more successful 
operation. The metal used in aircraft engine construction 



AIRCRAFT ENGINES 333 

is called upon to resist certain stresses, which may be divided 
as follows: tension, torsion, flexes, long column compression 
and short column compression. The ability of the metal to 
resist this stress is measured by its tensile strength, with 
exception of short column compression. For short column 
compression stresses castings will suffice. Heat treated 
alloyed steels are best in tensile strength, and therefore are 
good material for use in light weight parts subject to heavy 
stresses; cast iron and aluminum castings are good for low 
stresses in short column compression. Cylinders and pis- 
tons, owing to the stresses received, must be made accord- 
ingly. The cylinders have a tension applied to the extent 
of 10,000 pounds, and therefore should be made of steel; the 
piston receives only a short column compression stress, and 
therefore can be cast of aluminum. The frame or crankcase 
member is subjected to a bending and rotating stress; it 
should be made of aluminum and re-inforced with steel at 
the particularly stressed points. The bottom half of the 
case is unimportant. The crankshaft must be made of steel, 
therefore, its bearings must be either of bronze or babbitt, 
so that the shaft itself will be protected from wear. If 
bronze is used, the bearings must be carefully watched, and 
if babbitt is used, it must be fitted in a removable cap, that 
in turn is accurately fitted. This babbitt should be made in 
bushing form to do away with pouring. All moving parts, 
such as the piston, wrist pin, connecting rod, crankshaft, 
and camshaft, must be lubricated, and the metals that are 
in contact must be correctly related to one another. Steel 
cylinders have been found to be practical when soft pistons 
and rings are used. It must be remembered that different 
metals expand differently when heated to the same temper- 
ature; therefore, when two parts are in contact with one 
another they should be made of different metals, so that they 
will not expand equally and bind. Special care must be 



334 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 






exercised when fitting up an engine, so that the proper 
clearance will be allowed between the moving parts. It is 
always best to leave the clearance recommended by the 
manufacturer unless these are found by actual test to be 
incorrect. 

Q. 25. Why is lubrication necessary in aircraft engines? 

A. In any mechanism we have friction, which is a resisting 
force that tends to retard motion and bring all moving parts 
to a state of rest. We have noticed that about 5 per cent 
of the power the engine should develop is lost through fric- 
tion, and you can always tell that it is present by the heat 
which exists at bearings. Friction may be divided into two 
classes, rolling and sliding. In order to secure durability and 
successful operation, as well as a high percentage of mechan- 
ical efficiency in aircraft power plants, it is absolutely neces- 
sary to reduce friction to a minimum. Although to all 
appearances, a surface which has been machined and pol- 
ished, seems to be perfectly smooth, we would find it very 
rough if we should observe it through a microscope. When 
two surfaces are in contact with one another these minute 
projections have a tendency to cling to each other, unless an 
elastic oily substance is used to keep them apart. This oil 
spreads over all of the surface smoothing out the inequalities 
that produce heat and tend to retard motion. Rougher sur- 
faces have more friction than smoother ones, and soft bodies 
will produce more friction than hard ones. 

Q. 26. What kind of oils are best, and why? 

A . Oil derived from a petroleum base, able to pass a good 
cold test, having a high flash point, and showing a good 
viscosity is best for aircraft use. We have already learned 
that oil as well as acting as a lubricant, must serve as a 
thermal bridge or heat path. Therefore, it is necessary to 



AIRCRAFT ENGINES 335 

have an oil with a high flash point. We mean by this, that 
our oil can be heated to a very high temperature before it 
flashes and burns. Oil used in Aircraft engines must also be 
able to hold its body under high temperature, therefore, it 
must be viscous. Aircraft engines are operated under all 
conditions of temperature, therefore, it is necessary to have 
an oil that will flow freely in cold weather as well as in hot 
weather. Requirements may be briefly summarized as 
follows : 

1. It must have sufficient body to prevent the parts to 
which it is applied from seizing, but it must not be too viscous, 
in order to minimize the internal or fluid friction which exists 
between the particles of the lubricant itself. 

2. The lubricant must not gum (as in the case of asphaltum 
base oils) and it must not injure the parts to which it is 
applied by chemical action or injurious deposits. It should 
not evaporate rapidly. 

3. It should be selected, after a careful test, for the work 
for which it is intended, and must be a good conductor of 
heat. 

Q. 27. How many types of lubrication systems are used; 
which is best, and why? 

A. There are a number of different systems in use; the 
splash, the force splash system, and the full force feed. The 
splash system was commonly used in automobile practise, but 
owing to the fact that in the last few years the speed of auto- 
mobile engines has been increased, the system is no longer 
practicable. This system required an amount of oil to be 
carried in the case that would allow the connecting rod to 
dip into it. The rod would oil itself this way, and at the 
same time, due to its rotary motion, throw oil on the cylinder 
walls and on the wrist pin. There is no way of regulating 
this system in a satisfactory manner; therefore, it is con- 



336 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

demned for aircraft practise. The full force feed system 
with a dry sump is used quite extensively, and is considered 
best for aircraft engines, for oil is supplied at all angles, 
and under a constant pressure. The force splash operates 
in the same manner as the full force feed, with the exception 
that in the force splash system the cylinder walls and pistons 
are oiled by the splash from the connecting rods. The 
Liberty engine uses this system, therefore, shall be explained 
thoroughly later on. 

Q. 28. Why must an aircraft engine be cooled? 

A. It must be understood that the rapid combustion and 
continued series of explosions would soon cause the metal 
parts of an engine to become red hot, providing some means 
of taking some of this heat away were not supplied. The 
high temperature of these parts would burn away the oil 
and these parts would expand and seize, thereby wrecking 
the engine. Still another factor enters into engine cooling 
and that is, if the engine is allowed to run at too low a tem- 
perature, we lose a great amount of efficiency. Therefore, 
we can say the object of cooling is to keep the heat below 
the danger point, but at the same time have it high enough 
to secure the maximum amount of power to be received 
from the gasoline supplied. 

Q. 29. How many cooling systems are used; which is 
best, and why? 

A. There are two cooling systems used; air cooling and 
water cooling. Water cooling in turn is divided into two 
methods — the thermo syphon system, which operates under 
the theory that hot water rises and cold water falls, this 
causing circulation, and the force or pump system. Air 
cooling is considered inefficient and is never used on fixed 
types of aircraft engines. The thermo syphon system of 
water cooling is not positive enough for aircraft engines, 
therefore, the pump is used to circulate cooling water for 



AIRCRAFT ENGINES 337 

aircraft engines, and this system is best, as the water is 
circulated at a high velocity. All water cooled systems must 
have a radiator (or in other words, a combined storage and 
cooling tank), to cool the water after it has passed through 
the jackets. This radiator consists of two tanks mounted 
one above the other, and connected together by a series of 
pipes which may be round and provided with a number of 
thin fans to radiate the heat, or which may be flat in order 
to allow the water to pass through in thin sheets, in order 
that it will cool more easily. Radiators so designed are 
known as tubular radiators, and although they give very 
little trouble due to leakage, they are a trifle too heavy for 
aircraft use. A radiator which is composed of a large 
number of bent tubes, which expose a large area of the surface 
to the cooling influences of the draught of air caused by the 
forward motion of the machine, is known as a honeycomb or 
cellular radiator. While this type gives a lot of trouble 
from small leaks and is hard to repair, it is more efficient 
as a cooling medium, and fairly light in weight. The water 
is always taken from the bottom of the radiator, forced 
through a pump, and thence distributed equally to all 
cylinders. After passing through the jackets it is returned 
to the upper tank in the radiator, where it is broken into thin 
streams and allowed to filter to the bottom. By the time 
it arrives at the lower tank, it is sufficiently cool to be used 
again. The centrifugal type of circulating water pump is 
most commonly used, as it maintains a definite rate of circu- 
lation. It consists of an impellor of rotary form, which 
draws the water at a central point and forces it toward the 
outside. There are a number of items to be watched in 
connection with the cooling system of an aircraft engine. 
Our water service must be kept clear at all times. Only soft 
water should be used in the radiator. The temperature 
should never exceed 190 degrees, or should never be allowed 
to fall below 160 degrees. 



CHAPTER L 

Ignition Devices 

Q. 1. What fundamental units of electricity must be 
understood in conjunction with the study of ignition devices? 

A. These units are the volt, the ampere, the ohm, and the 
joule. 

Q. 2. What is the volt? 

A . The volt is the unit of pressure of electro motive force, 
necessary to force an ampere of current through a resistance 
of one ohm. It is expressed by the symbol (E). 

Q. 3. What is an ampere? 

A. The ampere is the amount of current that will flow 
through a resistance of one ohm, under the pressure of one 
volt. It is measured by an instrument called an ammeter, 
and is expressed by the symbol (I). 

Q. 4. What is the ohm? 

A. The ohm is the resistance through which the electro 
motive force of one volt will force a current of one ampere. 
It is expressed by the symbol (R). The ohm is also the 
resistance of 1000 feet of (B. & S.) copper wire. 

Q. 5. What is the joule? 

A. The joule is the unit of electrical work, and is the 
amount of work performed by a current of one ampere flowing 
for one second under a pressure of one volt. 

Q. 6. What is the electric power law? 

338 



IGNITION DEVICES 339 

A. One watt is the power delivered when an electro motive 
force of one volt, forces a current of one ampere through the 
circuit, and is expressed by the symbol (W) or IxE = W. 
746 watts are equal to 1 H.P. or 33,000 foot pounds in 1 
minute. 

Q. 7. What is the difference between insulators and 
conductors? 

A. Any material that obstructs the flow of current is 
called an insulator or insulating material. Any body that 
offers only a slight resistance to the flow of current is called 
a conductor. No conducting body possesses perfect con- 
ductivity but offers some resistance to the flow of current. 
Therefore, conductors can be divided into three classes: good 
conductors, fair conductors, and poor conductors. 

Q. 8. Name a few conductors, and insulators? 

A. Some good conductors are silver, copper, aluminum, 
zinc, and brass. Some fair conductors are, charcoal and 
coke, carbon plumbago, acid solutions, and sea water. Some 
poor conductors are water, the human body, flame, linen, 
dry woods, and marble. Insulators are, slate, oils, porcelain, 
dry leather and paper, wool, rubber, shellac, sealing wax, and 
silk. 

Q. 9. What is magnetism? 

A. Magnetism is a property possessed by certain sub- 
stances (lode stone, or leading stone, magnetic oxide of iron 
and others) and is manifested by its ability to attract and 
repel other materials susceptible to its effects. Magnetism 
may be produced in two ways. First, if a piece of steel is 
rubbed against another magnet, it will become magnetized 
and this is called magnetizing by contact. If this piece of 
steel is hard, it will retain this magnetism and thus become 



340 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



a permanent magnet. Secondly, if a piece of steel is brought 
within the fields of a powerful magnet, it will also become 
magnetized, this being called magnetizing by magnetic 
induction. Also if a powerful electric current flows through 
an insulating conductor wound around a piece of soft iron or 
steel, it will be magnetized, this being magnetizing by electric 
magnet induction. Usually an electro magnet is made up 
of soft material; therefore, it would lose its magnetism as 
soon as the current is turned off. 

Q. 10. Give a brief description of a magnet? 

A. Magnet is a piece of steel, or other magnetized sub- 
stance which possesses the properties of attracting other 
pieces of steel or iron, or other magnetizable bodies to it, 
and of pointing when freely suspended in a horizontal position 
toward the North Pole of the earth. 

Q. 11. What is meant by the term "pole," when used in 
connection with magnets? 

A . The ends of the magnet are termed its poles. The end 
which points toward the north geographical pole is the North 
Pole, and the other the South Pole. 



Q. 12. What two rules govern the generation of electric 
current? 
A. They are: 

1. If a conductor, or a number of conductors, are placed 
in a magnetic field and caused to revolve or rotate so as to 
cut the magnetic lines of force, a voltage will be generated. 
This is dependent upon the speed at which the lines of force 
are cut, and upon the number of lines of force cut, or the 
strength of the field. 

2. If a conductor, or number of conductors, are held 
stationary in a magnetic field and the field strength varied, 
a voltage will also be developed. This is dependent upon 



IGNITION DEVICES 341 

the speed at which the field strength is changed and the 
amount of change taking place. 

Q. 13. Define briefly an electric generator or dynamo? 

A . It is a machine for converting mechanical energy into 
electric energy by means of electromagnetic induction. It 
does not create electricity, but produces or generates an 
induced electromotive force, which causes a current to flow 
through a properly insulated system of electrical conductors 
external to it. 

Q. 14. Give a clear description of a generator or dynamo? 

A. It consists of two essential parts. First, a magnetic 
field produced by electro-magnets and a number of loops or 
coils of wire wound upon an iron core, forming an armature, 
and so arranged that the number of magnetic fines of force 
of the field threading through the coils will be constantly 
varied, thereby producing a continuous electromotive force. 

Q. 15. How are generator armatures wound? 

A. Generator armatures may be either lap wound or wave 
wound. Most generators are lap wound. When we say 
that a generator is lap wound, we mean that the commutator 
has an even number of bars, and the winding progresses from 
one bar to the adjacent, and so on until all bars are included. 
In wave wound generators, the commutator has an uneven 
number of bars, and the winding starts from one point touch- 
ing the bar on either side of what would be the center if we 
had an even number of bars. It continues in this manner 
until all the bars are included. If the second bar touched is 
past the center, it is called progressive wave winding. If it 
touches before the center it is retrogressive wave winding. 

Q. 16. Why must the output of a generator be controlled, 
and how is it done? 



342 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. We have noticed that the output of a generator is 
dependent upon the number of lines of magnetic force and 
the speed at which they are cut. Therefore, as the speed of 
the generator increases, the output increases, and as your 
batteries and ignition units are designed to carry so much 
current, they cannot take care of this overload. There are 
two ways of regulating the output of a generator, in order 
that it may deliver a constant supply of current at a given 
rate: 

1. A third brush is placed on the armature in such a way 
that its position ma}- be altered, so as to change the charging 
rate, as the output increases. The position may be either 
one-quarter, or one-half between the main brushes. The 
third brush is connected to a shunt in series with the field, 
and weakens the field as the speed increases. As it is moved 
toward the main brush adjacent to it, less current is collected 
by it, and the output is heavy. As it is moved away from 
the nearest main brush, it collects more current, and therefore 
weakens the field to the extent of causing the output to drop. 

2. By placing a controlling or regulating resistance in the 
field circuit, winch regulates the number of lines of magnetic 
force cut. 

Q. 17. Name some generator troubles, and their cause? 
A. 1. Low voltage generated due to: 

(a) Armature troubles — 

1. Speed too low controlled by engine. 

2. Open armature and flashing at commutator. 

3. Short circuited armature winding. 

(b) Field trouble — 

1. Field circuit open. 

2. Field coil grounded or short circuited. 

(c) Brush trouble — 

1. Brush off neutral. 

2. Brush off contact. 

Note: Brush tension is always given by manufacturer. 



IGNITION DEVICES 343 



(d) Generator sparks — 

1. Brushes off neutral. 

2. Brush tension low. 

3. Brushes sticking in holders. 

4. Brushes not trimmed. 

5. High mica 

6. Low mica. 

7. Soft brush causing duty commutator and 

sparking. 

8. Hard brush causing rough uneven com- 

mutator. 

9. Open armature coil. 

(e) Generator overheats (proper temp, under 150 

degrees F.). 

1. Commutator (anything causing sparking 

will cause overheating) . 

2. Brush tension too great. 

3. Armature (overload causing heat, due to 

some external short circuit). 

4. Fields overheat (short circuit). 
2. Heavy output. 

1. Regulator out of adjustment due to 
vibration. 



CHAPTER LI 
Storage Batteries 

Q. 18. What is a battery? 

A. When two dissimilar metals are placed partially sub- 
merged in an acid solution, which is capable of acting chem- 
ically upon one of them more than upon the other when 
they are connected by a wire, the combination constitutes a 
simple Voltaic cell. Correctly speaking, the word battery is 
applied to a number of such cells, although it is commonly 
applied to a single cell. 

Q. 19. How many kinds of batteries are used, and what 
are the advantages and disadvantages of each? 

A. There are two distinct types of cells or batteries, — the 
primary and secondary, the primary cells generally being 
dry cells, and in these the voltage falls rapidly, due to polar- 
ization from the chemical action, the active material being 
consumed, therefore, they cannot be used for ignition. The 
second set is comprised of secondary cells, accumulators or 
storage batteries, and their fundamental characteristic is that 
they can be recharged. The recharging being a conversion 
of one material into another, and in discharging the reverse 
taking place, causing a constant chemical action. 

Q. 20. Name the two different types of storage batteries, 
and the advantages of each? 

A. There are two different types, the Edison or alkaline, 
and the lead cell. The Edison cell has a very poor voltage 
regulation, although it is lighter and smaller. 

Q. 21. How many types of lead cells are used? 

344 



STORAGE BATTERIES 345 

A. There are two types, the Plante and Faure. The 
Faure is a heavy solid plate, while the Plante is a pasted 
plate. The Plante is more commonly used on account of 
lightness. 

Q. 22. How are the pasted plates constructed? 

A. The pasted plate has lead with 5 per cent antimony 
mechanically pressed into a grid, and is much stronger than 
the solid plate which is formed electrically. Lead peroxide 
(P Bo2) is pressed into the grid, and gives greater amperage 
with less weight than the solid plate. The negative plate 
is of a gray spongy lead. 

Q. 23. Give a general description of a storage battery? 

A . In order to give a clear description of a storage battery, 
we shall describe the Liberty battery. It is of the Plante 
lead plate type consisting of three positive and four negative 
plates to a cell, and has four cells capable of producing an 
E.M.F. (electric motive force) of 7.5 to 8.8 volts. There are 
certain structural differences incorporated in this battery to 
adapt it for aviation use. These plates are bound together 
by a lead lug, three positive plates and four negative plates 
making one element. The plates are separated from one 
another by thin pieces of wood, known as separators, and 
placed in a rubber jar resting on ridges about a half an inch 
from the bottom. The space left in the bottom is known as 
the mud cellar, and takes care of the gradual accumulation 
of sediment, which would cause a short circuit if it came into 
contact with the plates. The rubber jars containing the four 
elements are in turn encased in a strong wooden box,. Just 
above the plates there is a Baffle plate of hard rubber, and 
as the jar is about an inch and a half higher than the plates 
an air chamber is formed which prevents the electrolyte (acid 
and water) from spilling out when the battery is inverted. 



346 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

In the baffle plate there are several small holes to allow the 
electrolyte to seep in when filling. 

Q. 24. What happens when a battery is allowed to dis- 
charge below normal? 

A. Both plates become lead sulphate, which is a non- 
conductor, causing the plates to expand, short circuit, and 
warp, breaking the grids. 

Q. 25. What are the general causes of battery troubles? 
A. They are as follows: 

(a) Freezing. 

(b) Bad connections. 

(c) Grounds. 

(d) Impurities. 

(e) Sulphation. 

(f) Short circuited cells. 

(g) Hardened negatives, 
(h) Soft plates. 

Q. 26. Explain how these troubles would be corrected? 
A. (a) Freezing. The batteries will freeze at the following- 
temperatures if the specific gravity is as specified below: 

25° above zero 1050 

15° above zero 1115 

10° above zero 1140 

0° above zero 1165 

10° below zero 1190 

20° below zero 1205 

30° below zero 1220 

Note: These temperatures to be corrected to 70° F. (if temperature 

is above 70° add one point for every three degrees. If below 70° 

subtract one point for every 3 °. ) 



STORAGE BATTERIES 347 

(b) Bad connections. They result from copper sulphate 
forming on the terminals; the remedy is to keep them clean, 
washing them with ammonia, and using vaseline or asphal- 
tum paint as a preventative. 

(c) Grounds. If the electrolyte is spilled, there is a 
chance of grounding. Therefore, the battery should be 
wiped thoroughly dry with a rag saturated with ammonia, 
after testing for specific gravity. 

(d) Impurities. These consist of iron and copper sul- 
phate, the iron resulting from the use of undistilled water, 
and the copper sulphate from deposits on the terminal 
dropping into the cell. The remedy is to clean the cell. 

(e) Sulphation. It forms an insulation on the plates 
causing them to expand breaking the grids. The result of 
sulphation is a short circuited cell, and the remedy is never 
to let the battery run too low. If sulphation should set in a 
long slow charge from an external source should bring the 
battery back to normal. 

(f) Short circuited cells. This comes from active material 
dropped into the mud cellar. Overcharging forces the active 
material out of the grids. The remedy is to never over- 
charge, and if by accident this should occur, clean the cells. 

(g) Hardened negatives. These are caused by carrying 
electrolyte too low. Therefore, the plates must be always 
covered by the electrolyte. If the plates are removed they 
should be kept cool. 

(h) Soft plates. They are the result of overcharging, and 
can be remedied by placing the plates between two boards 
and squeezing them in a vise. This will force the active 
material back into the grids, and at the same time force the 
plate itself back into shape. 

Q. 27. What four rules govern the care and maintenance 
of storage batteries? 



348 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 






A. 1. Add nothing but pure water to the cells, and do it 
often enough to keep the plates covered. 

2. Take frequent hydrometer readings. 

3. Give the battery a special charge whenever the hydrom- 
eter readings show it to be necessary. 

4. Keep the filling plugs and connections tight and the 
battery clean. 

Q. 28. What precautions should be taken in mixing 
electrolyte? 

A. 1. Use a glass, china, earthenware, or lead vessel 
(never metallic other than lead). 

2. Carefully pour acid into the water, never water into acid. 

3. Stir thoroughly with wooden paddle and allow it to 
cool before reading the gravity. 

Q. 29. What is the object of charging a battery? 

A. The acid absorbed by the plates during discharge, is 
during charge driven from the plates by the charging current 
and restored to the electrolyte. No current from the charging 
source is ever stored in the battery. 

Q. 30. In what proportions should electrolyte be mixed? 
A. It should be mixed 3f parts distilled water to 1 part of 
chemically pure sulphuric acid. 

Note: Do not confuse the expression chemically pure (C. P.) with 
full strength. 

Sulphuric acid, oil of vitriol has a specific gravity of 1.835 
or 1.840, but the specific gravity is not always a measure of 
its purity. Sulphuric acid is heavier than water; therefore, 
the greater the proportion of acid contained in the electrolyte, 
the heavier the solution and the higher the gravity. 



STORAGE BATTERIES 349 

INDUCTION COILS AND DISTRIBUTORS 

Q. 31. Why are induction coils necessary in connection 
with battery generator systems? 

A. To cause the current to jump across a gap of one inch 
requires an extremery high voltage (about 50,000 volts) and 
as the voltage of the battery is very low (6 to 8 volts) it is 
evident that we must introduce some device into the circuit 
that will increase the voltage and consequently the jumping 
distance. 

Q. 32. Describe the induction coil? 

A. It consists of two separate and distinct coils, that are 
thoroughly insulated from each other. One has a few turns 
of heavy copper wire and is called the primary. The other 
consists of many thousands of turns of very fine copper wire, 
and is called the secondary. Both coils are wound around a 
bundle of soft iron wire called the "Core" from which they 
are carefully insulated. When the battery current flows 
through the primary coil, the core is magnetized and throws 
its magnetic influence through the turns of the secondary 
coil. The induced current depends upon: 

(a) The strength of the field or (the number of magnetic 
lines of force it contains). 

(b) The speed or rate of cutting or (the number of lines 
of force cut per second) . 

(c) The number of wires cutting the lines of force. In 
order to obtain a continuous discharge of sparks, and have 
this maximum density occur at the right moment, a set 
of breaker points is necessary. While these breaker points 
are not integral with the coil, their movement effects its 
operation. 

Q. 33. Describe the condenser as used in conjunction with 
the induction coil? 



350 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. When the breaker points open, breaking contact, it is 
necessary to reduce the spark to the lowest possible limits, 
in order to increase the life of the breaker points, and also 
in order to obtain as quick a break as possible. Therefore, 
the condenser is installed for the purpose of suppressing the 
spark between the breakers, and also to cause a sharp quick 
break in the primary circuit at the instant of the separation 
of the points. The intensity of the spark at the terminals 
of the secondary coil depends upon the quickness with which 
the break occurs, and if it were not for the condenser the 
length and intensity of spark would be greatly reduced. The 
condenser consists of alternate layers of paper and tinfoil, 
every other layer of tinfoil being connected to one side of the 
breaker and the remainder to the other. 

Q. 34. Why is a distributor necessary, and how does it 
function? 

A. After the high tension current is generated in the 
secondary winding, it must be transmitted to the proper 
cylinder at the proper time, and this is done through the 
medium of the distributor head. It is made of hard rubber, 
Bakelite or other insulating material with contact segments 
of brass interlaid and spaced at equal and proper intervals. 
A rotor arm directly connected to, or driven at the same 
speed as the camshaft (one-half engine speed) causes the 
high tension current to pass through these segments to the 
spark plug, through the medium of a high tension Ipad. 

Q. 35. Describe the Liberty ignition system by tracing the 
current from its source to the plug. 

A. The Delco (Dayton Engineering Laboratory Company) 
system as used on the Liberty engine is a single wire system. 
By this we mean that the negative side or ( — ) minus side 
of all units is grounded. To start the engine the switch 



STORAGE BATTERIES 351 

marked L (left) is moved outboard or to the On position. 
We do this, for there is less resistance in this switch. Either 
one, however, the right or left hand switch, could be used. 
The current leaves the positive side of the battery, flows 
through the ammeter, the ammeter showing a discharge. 
From the ammeter it flows through a lead to the primary 
binding post on either one of the distributor heads according 
to what switch is on (in this case the left one). It is then 
transmitted through the breaker points to the primary wind- 
ing of the induction coil (the condenser being in series with 
the breaker points and coil). As it is passed through the 
primary coil, a high tension voltage is induced into the 
secondary (there is no electrical connection between these 
two windings). We now have high tension current, and this 
is caused by a contact point from the coil to the rotor in 
the distributor, to the segments and thence to the spark 
plugs, and returned by ground. When our engine reaches 
the proper speed, at which the generator may produce more 
current than the battery is delivering both switches are 
thrown on. This speed is anywhere from 700 to 800 R.P.M., 
and can be determined by watching the ammeter. It is safe 
to leave both switches on when the needle passes over zero 
on the charge side. The proper way is to open the throttle 
to 700 or 800 R. P.M.— then throw the other switch, if 
ammeter shows charge, it is all right; if not, open throttle 
until it does for test. If it takes more than 700 to 800 
R.P.M. to show charge, we know that the regulator is not 
functioning properly. It can be adjusted by releasing the 
tension on the spring; however, it should not be adjusted 
unless one is thoroughly familiar with the operation. When 
both switches are on, the generator supplies both distributors 
and at the same time supplies the current to charge the 
battery. At full speed the ammeter should show from 4 to 
5 amperes charge. 



352 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. 36. What should be done periodically in the line of 
inspections and adjustments to insure proper operation of the 
Liberty Ignition system? 

A. 1. The battery should be flushed once a week and 
specific gravity tested. Remove vent plug, and fill each cell 
with distilled water to a height of 1 inch above the plates. 
Allow it to stand for a minimum of two minutes (not over 
five minutes), then remove all water in excess of what is 
required to just cover the plates. When the battery is fully 
charged, it should show a gravity of 1290 to 1310 degrees. 

2. Examine all wiring, both low tension and high tension, 
for broken insulation; also see that terminals are firmly 
attached. (Note : Instead of removing wires from conduits 
they can be tested with a magneto bell apparatus or buzzer. 
By attaching each end of the lead to the apparatus, the bell 
or buzzer can be rung. This shows whether or not the lead 
is broken or shorted.) 

3. Examine the surface of the distributor, particularly the 
path of the rotor brush and contact segments. Wipe out 
carbon dust with a soft rag, moistened with either alcohol, 
gasoline, or good metal polish. 

4. Examine distributor shaft for lost motion. There 
should not be more than x^-inch motion at the end of the 
rotor arm. 

5. Check gap of each breaker. It should be taken with 
breaker block on wide lobe of the cam. There should be 
10 to 13 thousandths (as shown by thickness gauge) clearance 
between them. If points are pitted they should be smoothed 
down on an oil stone 

6. Examine brushes. If they are less than J inch long, 
renew them. Brushes do not require lubrication. 

7. Examine the wire leading from the field coils to the 
generator terminal connections. This wire should be kept 
clean and free from oil and dirt. 



STORAGE BATTERIES 353 

8. Examine the commutator and brushes in the generator. 
If it is burned or rough, polish it off with a piece of very 
fine sand paper. When the commutator shows a fine blue 
polished surface it is in good condition and should only be 
wiped clean with a soft rag. 

9. It is important particularly in aircraft practice to see 
that all terminals are tight and above all clean. Oil, water 
and other liquids if allowed to remain on the insulation will 
saturate it, in time causing a short. Never try to adjust 
any apparatus that you do not fully understand. 



CHAPTER LII 
Magnetos 

Q. 37. Under what two principles do magnetos operate? 
A. Magnetos operate under the same principles that 
govern the operation of generators. 

1. If a conductor or a number of conductors are placed in 
a magnetic field, and revolved so as to cut the lines of force 
a voltage will be generated. 

2. If a conductor or a number of conductors are placed 
in a magnetic field, and the field strength varied so as to 
cut the windings, a voltage will also be generated. 

The first principle governs the operation of all shuttle 
wound armature types of magnetos, such as Bosch, Berling, 
Sims, and others. The second principle governs the opera- 
tion of the Dixie, and when applied to magnetos is known as 
the Mason principle. 

Q. 38. Describe the ordinary shuttle wound armature 
magneto? 

A. It consists of two permanent magnets (to supply the 
field) and iron core, upon which is wound both the primary 
and secondary windings, this assembly confusing the arma- 
ture. In series with the primary winding are a set of breaker 
points and a condenser, the operation of which we have 
already studied. A brush collects the high tension current 
from a collector ring. It is transmitted through a safety 
gap to a high tension pencil, and thence to the distributor. 

Q. 39. Describe the Dixie type of magneto? 
A. Like the ordinary shuttle type magneto the Dixie has 

354 



Magnetos 355 

two permanent magnets to supply the field. Two pole 
pieces mounted on a brass shaft are in contact with the north 
and south poles of the magnets. The primary and secondary 
windings are placed between the magnets and above the 
rotary pole structure. The condenser is mounted above the 
windings and the current is carried to the distributor through 
a high tension pencil as in all other magnetos. 

Q. 40. What advantages has the Dixie over all other types 
of magnetos? 

A . The windings of the Dixie magneto can be moved back 
and forth over the pole structures instead of advancing and 
retarding the breaker points; therefore, we receive the 
maximum density of spark at all speeds. This type of 
magneto can also use a four ring cam and can therefore be 
run at half speed of the other types, which allows a longer 
life and less trouble. The various working parts of a Dixie 
are very accessible and easily replaced. 

Q. 41. What points must be watched carefully for the 
maintenance of Dixie magnetos? 

A. The bearings should be lubricated after 1000 miles of 
flying, with a few drops of light oil. The breaker arm 
should also be lubricated after every 1000 miles, this oil being 
applied with a tooth pick. The proper clearance of the 
breaker points when separated should be 0.020 inch; these 
platinum contacts should be kept clean and properly adjusted. 
The distributor block should be removed occasionally and 
wiped free from carbon dust. ' Spark plugs used with this 
magneto should have a gap of 0.020 inch. The distributor 
absorbs moisture easily, and as a consequence will short when 
damp. Great care should be exercised in order to prevent 
this, and in k the event it should short due to its absorbing 
moisture it" can be dried out in an oven. 



356 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. 42. How would you time a Dixie magneto? 

A . We have seen from our study on ignition that the time 
of firing the plug is most important; therefore, the proper 
timing of the magneto is very important. The setting must 
be made in accordance with the valve timing and other 
characteristics of the engine it is to be used on. The follow- 
ing method must be carried out : 

1. Rotate the engine until piston in No. 1 cylinder is on 
upper dead center. Then reverse until piston is on firing 
position advanced. The rotor should be in the center of 
No. 1 segment and the breaker points should be just break- 
ing. Secure the magneto to its base and bolt coupling 
together. Connect each segment in the direction of rotation 
to the spark plugs in the cylinders in the proper order of 
their firing. It is well to check over timing, in order to be 
sure that it is correct. 

Q. 43. How would you synchronize two Dixie magnetos? 

A. That the two magnetos fire simultaneously is just as 
important as the timing of the magneto. The following 
method should be used: 

1. Remove the covers from the magnetos. 

2. Disconnect the primary wire from its binding post on 
both magnetos. 

Note: This will be found on the right hand side of the magneto. 

3. Connect each primary wire to a buzzer or light set, 
and ground this set. 

4. Rotate motor and note whether the lights, light, or 
buzzers work absolutely together. Note : If in an emergency 
buzzers or lights cannot be procured, cigarette papers can 
be used. They should be inserted between the breaker 
points and an equal tension should remove them if both 
magnetos are breaking together. 



CHAPTER LII1 
Gasolixe Carburetion and Carburetors 

Q. 1. Why is the study of gasoline and carburetors a very 
important matter in connection with aircraft engines? 

A . We have seen before that an internal combustion engine 
is a mechanical device for the conversion of the heat energy 
contained in gasoline to mechanical work. Therefore, the 
study of gasoline, its derivation, the proper mixing with air, 
and the apparatus with which we accomplish this mixing is 
very important. 

Q. 2. What differences in motor operation are caused by 
fuel and carburetors? 
A. They are: 

1. Differences in idling (which are important for maneu- 
vering). 

2. Differences in acceleration (also necessary for maneu- 
vering) . 

3. Differences as to steady load conditions, although spark 
and gas may be set. 

4. Differences in altitude. 

Therefore, a carburetor properly designed for use on air- 
craft engines must cause the engine to idle well and evenly. 
Must accelerate quickly but not spasmodic; must cause the 
engine to maintain an even speed under load, and should 
have some device attached in order that the pilot may com- 
pensate for atmospheric changes at high altitudes. 

Q. 3. What mechanical differences must be noted in 
designing a carburetor for aircraft use? 

357 



358 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. 1. Clogging. It must not clog easily from sand or dust 
or other small particles of solid matter, or gum and wax from 
gasoline itself. 

Note: This may also be remedied by filtering fuel thru fine screen 
and using a sediment trap on the line. 

2. Spilling. Gasoline should never spill from float cham- 
ber or valve, due to engine vibration. (This is a source of 
danger on account of fire.) 

3. Filtering. All aircraft are now maneuvered at excessive 
angles, therefore, the carburetor should function at any 
angle. 

4. Resistance to Backfire. Air valves in carburetors should 
be placed in such a manner that in the event of a backfire, 
the valve will not be blown shut. If the valve should be 
blown shut the carburetor will be broken off at the flange. 

Q. 4. How is gasoline procured and how can one tell good 
gasoline from poor? 

A. Gasoline is procured from crude petroleum, and 
petroleum gas, and it is distilled in two ways. 

1. Natural gas is compressed at a constant temperature, 
and condensed by being led through pipes surrounded by 
coils of water, known as the casing head process. 

2. Gasoline is distilled from crude petroleum by the frac- 
tional distillation process. The petroleum is boiled in a very 
large tank, and the various gases are led through pipes sur- 
rounded by coils of water to a number of smaller tanks. The 
gases passing off first form the best grade of gasoline, and so 
on down the line until we have heavy lubricating oil, and 
residue. From crude petroleum we get 8 to 10 per cent high 
grade volatile gasoline, 70 to 80 per cent in light oils such 
as kerosene and light lubricating oils. Heavy oil such as 
600 W and residue forming 5 to 9 per cent. Casing head 



GASOLINE CARBURETION AND CARBURETORS 359 

gasoline is a very volatile liquid showing a reading from 80° 
to 86° on the Baume hydrometer. It is best for engine use 
but the cost is prohibitive. It can be seen that the gasoline 
distilled from petroleum will contain a certain amount of 
kerosene and other objectional liquids, but still it is used in 
aircraft engines. This gasoline shows a reading of from 60° 
to 70° on the Baume hydrometer. Although the Baume 
reading will give a fair idea of the quality of the fuel, it is 
better in testing to redistill it and note the temperatures of 
the boiling points of its various constituents. This is known 
as fractional distillation and by plotting a curve, temperature 
against the quantity, the quality of the fuel can be judged. 

GASOLINE, VARIOUS GRADES, INSPECTION AND TESTS OF 

Q. How many grades of gasoline are used by the United 
States Navy 

A . Three grades, as follows : 

(A) Fighting aviation gasoline. 

(B) Domestic aviation gasoline. 

(C) Motor gasoline. 

Q. What are the detail requirements of the various grades 
of gasoline? 

A. (a) Grade A, fighting aviation gasoline, shall conform 
to the following requirements: 

1. Color. The color shall be water white. If specifically 
requested by the department, this grade shall be colored red. 

2. Doctor test. The gasoline shall yield a negative doctor 
test. 

8. Corrosion test. The gasoline when subjected to the 
corrosion test shall show no gray or black corrosion, and no 
weighable amount of deposit when evaporated in a polished 
copper dish. 



360 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

4-. Unsaturated hydrocarbons. Not more than 1 per cent 
of the gasoline shall be soluble in concentrated sulphuric acid. 

5. Add heat test. The gasoline shall not increase in tem- 
perature more than 10° F. 

6. Volatility and distillation range. When 5 per cent of 
the sample has been recovered in the graduated receiver, the 
thermometer shall not read more than 65° C. (149° F.) nor 
less than 50° C. (122° F.). 

When 50 per cent has been recovered in the receiver the 
thermometer shall not read more than 95° C. (203° F.). 

When 90 per cent has been recovered in the receiver the 
thermometer shall not read more than 125° C. (257° F.). 

When 96 per cent has been recovered in the receiver the 
thermometer shall not read more than 150° C. (302° F.), and 
the end point shall not be higher than 165° C. (329° F.). 

At least 96 per cent shall be recovered as distillate in the 
receiver from the distillation. 

The distillation loss shall not exceed 2 per cent when the 
residue in the flask is cooled and added to the distillate in 
the receiver. 

7. Acidity. The residue remaining in the flask after the 
distillation is completed shall not show an acid reaction. 

(b) Grade B, domestic aviation gasoline, shall conform to 
the following requirements: 

1. Color. The color shall be water white. 

2. Doctor test. The gasoline shall yield a negative doctor 
test. 

3. Corrosion test. The gasoline, when subjected to the 
corrosion test shall show no gray or black corrosion, and no 
weighable amount of deposit when evaporated in a polished 
copper dish. 

4- Unsaturated hydrocarbons. Not more than 1 per cent 

of the gasoline shall be soluble in concentrated sulphuric acid. 

5. Acid heat test. The gasoline shall not increase in tern- 



GASOLINE CARBURETION AND CARBURETORS 361 

perature more than 10° F. when subjected to the acid heat 
test. 

6. Volatilty and distillation range. When 5 per cent of 
the sample has been recovered in the graduated receiver, the 
thermometer shall not read more than 75° C. (167° F.), nor 
less than 50° C. (122° P.). 

When 50 per cent has been recovered in the receiver the 
thermometer shall not read more than 105° C. (221° F.). 

When 90 per cent has been recovered in the receiver the 
thermometer shall not read more than 155° C. (311° F.). 

When 96 per cent has been recovered in the receiver the 
thermometer shall not read more than 175° C. (347° F.). 

The end point shall not be higher than 190° C. (374° F.). 

At least 96 per cent shall be recovered in the receiver from 
the distillation. 

The distillation loss shall not exceed 2 per Cent when the 
residue in the flask is cooled and added to the distillate of 
the receiver. 

7. Acidity. The residue remaining in the flask after the 
distillation is completed shall not show an acid reaction. 

(c) Grade C, Motor Gasoline, shall conform to the follow- 
ing requirements: 

1. Distillation range. When the first drop has been 
recovered in the graduated receiver, the thermometer shall 
not read more than 60° C (140° F.). 

When 20 per cent has been recovered in the receiver the 
thermometer shall not read more than 105° C. (221° F.). 

When 50 per cent has been recovered in the receiver the 
thermometer shall not read more than 140° C. (284° F.). 

When 90 per cent has been recovered in the receiver the 
thermometer shall not read more than 190° C. (374° F.). 

The end point shall not be higher than 225 C.° (437° F.). 

At least 95 per cent shall be recovered as distillate in the 
receiver from the distillation. 



362 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

METHODS OF INSPECTION, TESTS, ETC. 

(a) All gasoline shall be inspected before acceptance. 
Several samples consisting of at least 100 cc. each shall be 
taken from each shipment. These samples immediately 
after drawing shall be retained in a clean, absolutely tight 
closed vessel and the sample for test taken from the mixture 
directly into the test vessel. 

(b) Color. One hundred cubic centimeters of the gasoline 
contained in a 4-ounce sample bottle or a graduate shall be 
compared to a similar column of distilled water. 

c. Doctor test. 

1. Preparation of reagents — Sodium plumbite or "doctor 
solution" Dissolve approximately 125 grams of sodium 
hydroxide (NaOH) in a liter of distilled water. Add 60 to 
70 grams of litharge (PbO) and shake vigorously for 15 to 
30 minutes, or let stand with occasional shaking for at least 
a day. Allow to settle and decant or siphon off the clear 
liquid. Filtration through a mat of asbestos may be 
employed if the solution does not settle clear. The solution 
should be kept in a bottle tightly stoppered with a cork. 

2. Sulphur. Pure flowers of sulphur. 

3. Making of test. Shake vigorously together two volumes 
of gasoline and one volume of the "doctor solution" (10 cc. 
of gasoline and 5 cc. of "doctor solution") in an ordinary 
test tube; or proportional quantities in a 4-ounce oil sample 
bottle may conveniently be used. After shaking for about 
15 seconds, a small pinch of flowers of sulphur should be 
added and the tube again shaken for 15 seconds and allowed 
to settle. The quantity of sulphur used should be such that 
practically all of the sulphur floats on the surface separating 
the gasoline from the "doctor solution." 

4. Interpretation of results. If the gasoline is discolored, 
or if sulphur film is so dark that its yellow color is noticeably 
masked, the test shall be reported as positive and the gasoline 



GASOLINE CARBURETION AND CARBURETORS 363 

condemned as "sour." If the liquid remains unchanged in 
color and if the sulphur film is bright yellow or only slightly 
discolored with gray or flecked with black the test shall be 
reported negative and the gasoline considered "sweet." 

(d) Corrosion test. 

1. The apparatus used in this test consists of a freshly 
polished hemispherical dish of spun copper, approximately 
3| inches in diameter. 

2. Place 100 cc. of the gasoline to be examined in the dish, 
and place the dish in an opening of an actively boiling 
steam bath so that the steam comes in contact with the 
outer surface of the dish up to the level of the gasoline. 
Leave the dish on the steam bath until all volatile portions 
have disappeared. 

3. Interpretation of results. If the gasoline contains any 
dissolved elementary sulphur the bottom of the dish will 
be colored gray or black. 

If the gasoline contains undesirable gum-forming con- 
stituents, there will be a weighable amount of gum deposited 
on the dish. 

Acid residues will show as gum in this test. 

(e) Unsaturated hydrocarbons. 

1. The apparatus used in this test consists of a modified 
Babcock bottle. The neck is calibrated for the volume of 
10 cc, subdivided in 0.2 cc. intervals. The bottle shall 
contain approximately 30 cc. up to the base of the neck 
and shall be approximately 6f inches high over all. 

2. Ten cubic centimeters of the gasoline to be tested is 
run from a pipette into a clean, dry bottle, cooled for a 
minute or two by immersing in ice water, and then 20 cc. 
of commercial 66° sulphuric acid (containing approximately 
93.19 per cent H 2 S0 4 ) is poured in from a small graduate. 
Care should be taken that the acid runs quietly down the 
side of the bottle, instead of splashing onto the surface of 



364 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

the gasoline. A rubber stopper is then placed in the bottle 
and the contents are shaken, first slowly, then vigorously 
with a rotary motion for several minutes. The gasoline 
and the acid are separated by either one of the following 
two methods: 

(f) Gravity separation. Sulphuric acid is added to the 
contents of the bottle until the surface of the liquid is about 
level with the upper graduation mark on the neck of the 
bottle. The mixture is then set aside and allowed to stand 
overnight, when practically complete separation is effected. 

(g) Centrifugal separation. The stoppered bottle is 
placed in a suitable centrifuge and revolved for two or three 
minutes at a speed of 500 to 1,000 r.p.m. Sufficient acid 
is then added to bring the level up to the lower graduation 
mark and the contents are again centrifuged to complete 
the separation. More acid is then added to bring the 
column to the upper graduation mark, after which the 
residual volume of the gasoline is read. 

(h) Acid heat test. 

1. Apparatus. One 1-pint glass bottle provided with a 
ground-glass stopper. 

One 50 cc. graduate. 

One thermometer graduated in 1° divisions. (The ther- 
mometer used in taking pour test of lubricating oils is 
perfectly satisfactory) . 

2. Method of testing. Pour 150 cubic centimeters of the 
gasoline into the pint bottle. 

Pour 30° cubic centimeters of 66° commercial sulphuric 
acid, containing approximately 93.19 per cent H 2 S0 4 into 
the graduate. 

Bring both solutions to the room temperature and note 
the temperature. 

Pour the acid into the bottle containing the gasoline, 
insert ground-glass stopper, and shake vigorously for 2 



GASOLINE CARBURETI0N AND CABRURETORS 



365 



minutes. (Avoid warming the bottle from the heat of the 
hands). 

Allow to stand for 1 minute, then remove stopper, insert 
the thermometer and note the temperature of the gasoline. 

The difference between the two readings represents the 
raise in degrees. 

(i) Flash test. This test is the same as that specified in 
the methods of testing burning oils. 

(j) Spot test. Place 5 drops of the oil on clean white filter 
paper and allow the liquid to evaporate at room tempera- 
ture, away from direct sunlight. There should be no oily 
spot left after 30 minutes. 

(k) Distillation test. Apparatus. 1. Distillation flask and 
support. 

The flask used shall be the standard 100 cc. English flask, 
described in the various textbooks on petroleum. Dimen- 
sions are as follows: 



DIMENSIONS 


CENTI- 
METERS 


TOLER- 
ANCE 


I'NCHES 


TOLER- 
ANCE 


Outside diameter of bulb 

Inside diameter of neck 

Length of neck 


6.5 

1.6 

15.0 

10.0 

0.6 


±0.10 
±0.05 
±0.20 
±0.20 

±0.05 


2.56 
0.63 
5.91 
3.94 

0.24 


±0.04 
±0.02 
±0.08 


Length of vapor tube 

Outside diameter of vapor 
tube 


±0.08 
±0.02 







Position of vapor tube, 9 cm. (3.55 inches) above the 
surface of the gasoline when the flask contains its charge 
of 100 cc. The tube is approximately in the middle of 
the neck, and is set at an angle of 75° from the perpendicu- 
lar. The observance of the prescribed dimensions is con- 
sidered essential to the attainment of uniformity of results. 

The flask shall be supported on a piece of asbestos board 
6 inches square having a circular opening 1J inches in 



366 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

diameter; this means that only this limited portion of the 
flask is to be heated. The use of wire gauze is forbidden. 

(1) Thermometer. The thermometer shall be made of 
selected enamel-backed tubing, having a diameter between 
5.5 and 7 mm. The bulb shall be of Jena normal or Corning 
normal glass; its diameter shall be less than that of the 
stem, and its length between 10 and 15 mm. The range 
shall cover 0° C. (32° F.) to 270° C. (518° F.) with 
the length of the graduated portion between the limits of 
210 to 250 mm. The point marking a temperature of 35° C. 
(95° F.) shall not be less than 110 mm. nor more than 135 
mm. from the bottom of the bulb. 

When the thermometer is made according to the Centi- 
grade scale it shall be graduated in 1° intervals. Each 
tenth degree shall be numbered and each fifth degree shall 
be distinguished by a larger mark. 

When made according to the Fahrenheit scale, it shall 
be graduated in 2° intervals, each twentieth degree being 
numbered and each tenth degree being distinguished by a 
larger mark. 

The scale shall be graduated for total immersion. The 
accuracy shall be within about 0.5° C. (1.0° F.). The space 
above the meniscus shall be filled with an inert gas, such 
as nitrogen, and the stem and bulb shall be thoroughly aged 
and annealed before being graduated. 

All materials and workmanship shall be the best. 

(m) Condenser. The condenser shall consist of a thin- 
walled tube of brass or copper \ inch internal diameter and 
22 inches long. It shall be set at an angle of 75° from the 
perpendicular and shall be surrounded with a cooling jacket 
of the trough type. The lower end of the condenser shall be 
cut off at an acute angle and shall be curved down for a 
length of 3 inches. The condenser jacket shall be 15 inches 
long. 



GASOLINE CARBURETION AND CARBURETORS 367 

(n) Graduate The graduate shall be of the usual type with 
a pressed or molded base and a lipped top. The graduated 
portion shall be for the quantity of 100 cc. It shall be 
numbered from the bottom up at intervals of 10 cc. Mark- 
ings shall be for single cubic centimeters and each fifth 
mark shall be distinguished by a longer line. 

The length of the graduated portion shall be not less than 
7 inches nor more than 8 inches. The distance from the 
upper graduated mark to the rim shall be not less than If 
inches nor more than li inches. 

(o) Source of heat. The source of heat in distilling gasoline 
may be a gas burner, an alcohol lamp, or an electric heater. 

(p) Procedure and details of manipulation z'n conducting 
distillations. (1) The condenser trough is filled with water 
containing a liberal portion of cracked ice, so that the tem- 
perature is not lower than 32° F. nor above 40° F. The 
condenser tube is swabbed to remove any liquid remaining 
from a previous distillation. 

(2) One hundred cubic centimeters of gasoline is measured 
at a temperature of 60° F. into the clean, dry Engler flask 
from a 100 cc. graduate. The same graduate is used as a 
receiver for distillates without any drying. This procedure 
eliminates errors due to incorrect sealing of graduates and 
also avoids the creation of an apparent distillation loss due 
to the impossibility of draining the gasoline entirely from the 
graduate. 

(3) The above-mentioned graduate is placed under the 
lower end of the condenser tube so that the latter extends 
downward below the top of the graduate at least 1 inch. If 
the room temperature be above 80° F. the receiving graduate 
shall be placed in a bath maintained at a temperature not 
less than 65° F. nor more than 75° F. The condenser tube 
shall be so shaped and bent that the tip can touch the wall 
of the graduate on the side adjacent to the condenser box. 



368 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

This detail permits distillates to run down the side of the 
graduate and avoids disturbance of the meniscus caused by 
the falling of drops. During the distillation the graduate is 
moved occasionally to permit the operator to ascertain that 
the speed of distillation is right, as indicated by the rate at 
which drops fall. The proper rate is from 4 cc. to 5 cc. per 
minute, which is approximately two drops a second. The 
top of the graduate is covered, preferably by several thick- 
nesses of filter paper or blotting paper, the condenser tube 
passing through a snugly fitting opening. This minimizes 
losses due to circulation of air through the graduate and also 
excludes any water that may drip down the outside of the 
condenser tube on account of condensation on the ice-cooled 
condenser box. 

(4) A boiling stome (a piece of ungiazed porcelain or other 
similar material not exceeding J inch in any dimension) is 
dropped into the gasoline in the Engler flask. The ther- 
mometer is equipped with a well-fitted cork and its bulb 
covered with a thin film of absorbent cotton (preferably the 
long-fibered variety used for surgical dressing). The quan- 
tity of cotton used shall be not less than 0.005 nor more than 
0.010 gram (5 to 10 mgm.). The thermometer is fitted into 
the flask with the top of the bulb just below the lower level 
of the side neck opening. The flask is connected with the 
condenser tube by means of a well-fitted cork or stuffing 
box. The vapor tube must extend at least | inches into the 
condenser tube. 

(5) Heat must be so applied that the first drop of the 
gasoline falls from the end of the condenser tube in not less 
than 5 nor more than 10 minutes. The initial boiling point 
is the temperature shown by the thermometer when the first 
drop falls from the end of the condenser tube into the grad- 
uate. The amount of heat is then increased so that the 
distillation proceeds at a rate of from 4 cc. to 5 cc. per minute. 
The thermometer is read as each of the selected percentage 



GASOLINE CARBURETION AND CARBURETORS 369 

marks is reached. The maximum boiling point or end point 
is determined by continuing the heating until the column of 
mercury reaches a maximum and then starts to recede 
consistently. 

(6) Distillation loss is determined as follows: The con- 
denser tube is allowed to drain for at least 5 minutes after 
heat is shut off, and a final reading taken of the quantity of 
distillate collected in the receiving graduate. The dis- 
tillation flask is removed from the condenser and thoroughly 
cooled as soon as it can be handled The condensed residue 
is poured into a small graduate or graduated test tube and 
its volume measured. The sum of its volume and the volume 
collected in the receiving graduate, subtracted from 100 cc, 
gives the figure for distillation loss. 

(q) Acidity. The cooled residue from the distillation flask 
is collected in a test tube and its volume noted. Three 
volumes of distilled water are added and the tube is shaken 
thoroughly. The mixture is allowed to separate and the 
aqueous layer is removed to a clean test tube by means of a 
pipette and 1 drop of a 1 per cent solution of methyl orange 
is added. No pink or red color shall be formed. 

PACKING AND MARKING OF SHIPMENTS 

(7) Gasoline shall be delivered in containers in conformity 
with the issue of Navy Department Specification 42D2 in 
effect at the date of opening of the bids. Each container 
shall be marked with the grade of gasoline (fighting aviation, 
domestic aviation, or motor), quantity contained, contract 
or order number, and name of the contractors. 

Q. 5. What is a carburetor? 

A. A carburetor is a device for mixing air and gasoline in 
the proper proportions (about 15 or 16 parts of air to one 
part of gasoline) in order that it may form an explosable 
mixture. 



370 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. 6. Describe some early forms of carburetors or 
vaporizors. 

A. These early forms of carburetors or vaporizors were 
very crude and cumbersome, the mixing of the gasoline and 
air being accomplished in three ways. 

1. The air stream was passed over the surface of the liquid, 
this being known as a surface carburetor (now obsolete) . 

2. The air was passed through loosely placed absorbent 
material saturated with gasoline, this being known as the 
"wick" carburetor (also absolete). 

3. The air was passed directly through the gasoline, this 
being known as the "bubbling" carburetor. 

These old type carburetors functioned fairjy well on low 
speed engines, for they used a gasoline high in volatility. 
The modern high speed engine is required to use low grade 
fuel, so the old type of carburetor has given way to the 
device known as the "spraying carburetor," which reduces 
the fuel to a spray by the suction effect of the entering air 
stream drawing it through a small opening. 

Q. 7. Describe the modern float feed carburetor. 

A. The modern "spraying" carburetor is provided with 
two chambers; one the mixing chamber, through which the 
air stream passes mixing with the gasoline, and the other in 
which a constant level of fuel is maintained by a simple float 
and float valve mechanism. A jet or standpipe is placed in 
the middle of the mixing chamber to carry the fuel, and the 
object of the float is to maintain that level of gas that will 
not overflow when the motor is stopped. 

Q. 8. What is one of the hard problems that effect 
carburetion? 

A. It is generally believed that the flow of gasoline and 
air increase proportionately when the motor "is opened up" 



GASOLINE CARBURETION AND CARBURETORS 371 

and the speed increased. But such is not the case, for the 
flow of gasoline increases faster than the flow of air. Most 
carburetors have automatic valves and other mechanical 
devices to compensate for this, but so far the Zenith car- 
buretor regulates the flow of gasoline and air in the simplest 
manner, and therefore is used extensively on aircraft engines. 

Q. 9. Describe the Zenith carburetor. 

A. To best illustrate the principle of the Zenith car- 
buretor, we must first consider the elementary type of car- 
buretor, one with two chambers, the float chamber and the 
mixing chamber. We have seen that as the suction increases, 
the flow of gasoline also increases, but to a greater extent 
than the flow of air. By using a number of auxiliary air 
valves we can dilute this rich mixture by adding air, but 
the trouble caused by these moving parts can be eliminated 
by the use of the compound nozzle and compensating jet. 
With our first carburetor, with the single jet, which causes 
the mixture to grow richer and richer as the speed increases, 
is combined another apparatus integral with it which causes 
the mixture to grow leaner as the speed increases. These 
two devices combined in one carburetor balance, which gives 
us a desirable mixture (15 to 16 parts of *air to one of gas 
constantly). This second jet, causing the mixture to grow 
lean as speed increases is known as the compensating device. 
A certain fixed amount of gasoline (determined by the size 
of the opening in the float chamber) is permitted to flow by 
gravity into a well open to the atmosphere. The suction at 
the top of the jet in the mixing chamber has no effect upon 
the flow through this opening or compensator in the float 
chamber, for the suction is destroyed by the well open to 
the atmosphere. Therefore, when motor suction increases 
drawing more air through the carburetor, the amount of 
gasoline remains the same, consequently the mixture grows 



372 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

poorer. The Zenith carburetor is therefore a combination of 
two carburetors in one. One in which the mixture grows 
rich, and one which grows poor as speed increases; therefore, 
from the cranking of the engine to its highest speed there is a 
constant ratio of air and gasoline to supply efficient combus- 
tion. In addition to this compound, nozzle or compensating 
device, the Zenith carburetor is equipped with a starting 
and idling device. There is a priming hole above the mixing 
chamber just at the edge of butterfly valve, where the suction 
is greatest when this valve is closed or very slightly open. 
The gasoline is drawn up by the suction through the priming 
hole and mixed with the air rushing by the butterfly valve 
giving an ideal or rich mixture for starting and idling. At 
high speeds when the butterfly valve is opened, this idling 
device ceases to operate, because the gasoline in this well is 
drawn through the cap jet. 

Q. 10. What three parts have to be changed in the 
Zenith carburetor in order to change its adjustment? 

A. They are choke tube or venturi tube, main jet and 
compensator. The size number of each of these parts is 
stamped on the end of each part, and all three parts together 
form the "setting." 

Q. 11. How are chokes of venturi tubes numbered? 
A. The chokes are numbered in millimeters according to 
the size of their smallest diameter. 

Q. 12. How are jets and compensators numbered? 

A . The jets and compensators are numbered in hundredths 
of a millimeter. A one hundred jet has a one millimeter 
hole, and is smaller than a one hundred and five jet. They 
are graded by five hundredths of a millimeter apart. 



GASOLINE CARBTJRETION AND CARBURETORS 373 

Q. 13. What particular fact should be borne in mind when 
altering the "setting" of the Zenith carburetor? 

A. When engines are regularly equipped at the factory 
with the Zenith carburetor, it is seldom necessary to change 
the factory setting, for these have always been determined 
by experts after conducting many tests. There is no moving 
part in this carburetor that affects the mixture, so it is 
always reasonable to assume that trouble may be caused 
by dirt and water in carburetor, by some one tampering 
with its setting, or by some disarrangement of adjustment of 
ignition, valve operation, or other mechanism. 

Q. 14. How should a test be made to ascertain whether 
or not the setting is incorrect. 

A. The following tests should be made in order first 
determining whether the faults lie in the choke, then the 
main jet, and then the compensator. 

1. Choke. This is a venturi tube with an angle of 10° on 
the discharge side, and is of a streamline shape that allows 
the maximum flow of air without any eddies and with the 
least resistance. This choke is held in place with a single 
screw and easily removed, providing the butterfly valve 
(throttle) is not in place. 

(a) If pick up is defective and cannot be bettered with a 
larger compensator. If motor does not run smooth at idling 
speed. If motor shows a tendency to load up at high speeds 
and misses, our choke tube is too large. 

(b) If the motor does not take a full charge with open 
throttle, and if although "pick up" is good maximum R.P.M. 
is not obtained, the choke tube is too small. Remember 
that when a larger choke tube is used, a greater amount of 
air is admitted and the mixture grows leaner. 

2. Main jet. It is easily removed after unscrewing the 
lower plug. The influence of the main jet is mostly felt at 
high speeds. 



374 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

(a) Main jet too large. While running at high speed our 
engine will have all indications of a rich mixture. 

(b) Main jet too small. The mixture will be lean at high 
speeds, and the maximum R.P.M. will not be received. 

3. Compensator. It is easily removed after unscrewing the 
lower plug. The influence of the compensator is noted 
generally at low speeds. A pull under a load generally shows 
whether or not the compensator is of the correct size. 

(a) Compensator too large. Too rich a mixture on a hard 
pull will be noted in operation, or the same indications of a 
rich mixture at high speeds. 

(b) Compensator too small. Our engine will show a lean 
mixture, missing and backfiring. 

4. Idling devices. This device differs in each model of 
carburetor. Before adjusting this device, it must be remem- 
bered that many factors prevent good idling. Some are: 

1. Poor gaskets 

2. Loose valve stems [■ creating air leaks. 

3. Pitted valves J 

4. Leaky plugs or primers. 

5. Spark plug gap too close. 

6. Load too light. 

7. Too much spark advance. 

8. Spark too late. 

(a) If idling device is too small. It will be impossible to 
obtain the proper mixture, except by turning the idling screw 
all the way in. (In this event use a larger idling device.) 

(b) If idling device is too large. It will be impossible to 
obtain the proper mixture except by turning the idling screw 
out as far as possible. (In this event use a smaller idling 
device.) 

Q. 15. Name some carburetor or gasoline troubles and 
their remedy. 



n 



GASOLINE CARBURETION AND CARBURETORS 375 

A. 1. If engine starts hard. 

(a) Be certain that throttle is opened a trifle. 

2. See if there is fuel in carburetor. (This can be done 
by depressing the needle valve in the float chamber. If float 
chamber is empty, examine supply tank. If empty fill with 
gasoline; if it has a sufficient amount of fuel, examine pipes 
for dirt and other matter that may be "stopping up" the 
line. 

3. Check up ignition (take off a spark plug wire and 
hold it about J inch from the plug; if no spark is received 
check up ignition. 

Note: (The above examinations will show whether or not you have 
fuel for your engine, and the proper spark to ignite it. ) In the event 
that we have both, look for further trouble as follows : 

Note: The following troubles cannot be termed carburetortroubles, 
but as a general rule the carburetor is blamed for troubles emanating 
from other sources. 

4. Leaks in the manifold or its connections. These leaks 
are generally found at the joints, and are usually caused by 
faulty gaskets, by the absence of gaskets, or by the failure 
of the joints to come squarely together. 

Note : (Gaskets should be made of some soft compressible material) 
preferably a good gasket paper. Rubber should never be used on a 
fitting, holding gasoline.) In rare cases a manifold will leak air, 
due to a flaw in the casting. 

5. Worn valve stems and guides. This is a trouble 
peculiar to old engines, and as a rule is hard to find. In the 
case that no leaks are found in the manifold or its connec- 
tions, an engine still gives trouble from too much air, test 
valve stems and guides. Remember an air leak, however 
small it may seem to be, will have a great effect on engine 
starting, and operation, at low speeds. 



376 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

6. Priming. After the above has been done, remove 
spark plugs and pour a few drops of gasoline in each cylinder. 
If the motor starts, but runs just long enough to burn up 
the priming charge, see if your idling device has not been 
plugged with dirt. 

7. When the engine does not idle well. Before adjusting 
the carburetor it should be remembered, that in order to 
obtain good results in idling, the engine must be in good 
condition, and in perfect adjustment. Ignition must be 
strong and valves must seat good and have proper clearance. 
All cylinders must have equal compression and there must 
not be any air leaks however small. ' 

Note: Never adjust the carburetor unless the engine is warm. 

If mixture is rich while idling, it can be noted by missing 
and heavy gases coming from exhaust. Screw out on idling 
device until engine runs smooth. 

If mixture is lean while idling it will be noted by missing, 
back-firing, and in some cases stopping. Screw in on adjust- 
ing device until regular running is obtained. 

Note : When making an idling adjustment have it on the ' ' rich side . ' ' 
i.e., have the screw adjusted to such a point that a slight turn in 
would result in a rich mixture. 

8. When "pick up" is defective, it may be caused by 
any of the following: Mixture too rich, or too lean, spark 
plug points too far apart, manifold too large, or having 
a rough interior. If our adjustment is lean and the throttle 
is pulled open suddenly the engine will hesitate, spitback, 
and stop. (Try a larger main jet.) If carburetor is adjusted 
rich, and the throttle is pulled open suddenly the engine 
will hesitate and then run in an irregular manner. (Try a 
smaller main jet or compensator.) If changing jets does 



GASOLINE CARBURETION AND CARBURETORS 377 

not correct matters then change the choke, selecting jets 
accordingly. 

Note: The only time a knock can ever be caused by a carburetor, 
is when an engine is pulling under a heavy load at low speeds; this 
knock is due to too lean a mixture. 

Q. 16. What are the causes of leaking carburetors, and 
how can it be remedied? 

A. A carburetor leaks fuel, it will be noted when gasoline 
is found to be dripping from the carburetor. In this event 
the carburetor should be removed from the engine and care- 
fully examined as follows : 

The bottom plugs, filter plugs, channel screws and cap jet; 
there are fibre washers under each of these that may have 
become defective, and they can be easily replaced with 
new ones. 

Leaking carburetors are sometimes caused by some dis- 
arrangement within the float chamber. Before attempting 
to regulate or change the level of the fuel in the float chamber 
the mechanician should be satisfied that the leakage is due 
to this fault. Remove the float and shake it to determine 
whether or not any fuel has leaked into it. If so, submerge 
the float in boiling water. This will vaporize what fuel has 
leaked into the float, and at the same time locate the hole, 
as the fuel will come out at that place, causing bubbles to 
appear. When soldering the float only heat it to the point 
that is necessary in order to solder it, and use only enough 
solder to plug the hole, for if it is heated too hot the float 
will be damaged beyond repair, and if too much solder is 
used it will lose its buoyancy. Dirt or other foreign matter 
under the seat of the needle valve will also cause leakage. 
This can generally be remedied by twisting the needle, while 
alternately raising and lowering it. Leakage may also be 
caused by valve lever weights wearing flat. By reversing 
these members, this trouble can be remedied. 



378 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. 17. How should a carburetor be cleaned? 

A. Most carburetor troubles are caused by water in the 
gasoline. The quickest way to remedy this trouble is to 
drain the carburetor. When the jets become clogged with 
dirt, there is a possibility of cleaning them by running the 
motor fast, i.e., accelerating a few times from idling to full 
speed. If the carburetor is so dirty that the jets have to be 
removed, they can be cleaned by air, or by a soft piece of 
wire (never use a cutting tool or any object that will burr them 
or change their size. 

Note: The straining of the gasoline will do away with most troubles 
caused by dirt; however, some poor grades of gasoline contain some 
amount of wax and gum that will cause trouble at times. 



CHAPTER LIV 
Aircraft Engine Troubles 

Q. 1. How are aircraft engine troubles located? 

A. The first step toward the location of engine trouble is 
to thoroughly familiarize yourself with engine construction, 
that is learn each part, its function, and its relation to other 
parts. Trouble must be found through a process of elimina- 
tion. The engine can be divided into two classes, the struc- 
ture itself, which includes the crankcase, bearings, crank- 
shaft, camshaft, connecting rods, pistons, cylinders, valves 
and their operating gear; and the auxiliaries which include 
the ignition system, the cooling system, the gasoline supply 
and vaporizing devices, and the lubrication system. These 
various appliances are so closely related to one another that 
the defective action of any one may interrupt the operation 
of the entire engine. Some of the parts are more important 
than others, but each one is essential and its faulty operation 
(especially the auxiliaries) will show up soon. 

Q. 2. How would you divide or classify engine troubles? 
A . Troubles can be classified in the following way : 

1. Those that cause a complete stoppage. 

2. luose that cause missing and poor operation. 

3. Those that cause noisy operation or knocking. 

4. Those that cause loss of power and overheating. 

5. Failures to start. 

Q. 3. Name some troubles that would cause a complete 
stoppage, their symptoms and remedy? 

A. Troubles that cause complete stoppage can in turn 
be divided into two classes; troubles originating within the 

379 



380 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

engine or structure, and troubles originating within the 
auxiliaries. 

1. Structure troubles that cause complete stoppages are 
generally breaking of parts, and are easy to find. The 
breaking of a crankshaft, camshaft, connecting rod, cylinder, 
piston, or the like will cause stoppage. 

2. Auxiliary troubles that cause stoppage are not as easily 
found, therefore, we shall incorporate the most important 
ones in chart form. 

Note: It should be remembered that if a part should break, we must 
not jump at conclusions, and say that the trouble originated in that 
particular part, for such is not the case. For example, a crankshaft 
breaks, due to seizing at one particular bearing. It is evident then, 
that this bearing was not receiving oil. We must then trace our 
trouble to the oil passage, and see whether or not it was abroken lead 
or a plugged outlet. 



AIRCRAFT EXGIXE TROUBLES 



381 



Auxiliary troubles that cause stoppage 



Engine not receiving gaso- 
line 



Engine not receiving gaso- 
line 



Engine not receiving spark 



Engine not receiving spark 



Engine not receiving spark 



Engine broken or parts 
broken 



Xo gasoline in carburetor 



Gas in carburetor but not 
getting to engine 



Xo spark when wire is re- 
moved from plug and held 
close to cvlinder 



Xo spark when wire is re- 
moved from plug and held 
close to cylinder 



If spark is received when 
wire is removed from 
plug, and held close to 
cylinder 

Sudden stoppage, accompa- 
nied by metallic sound 



Fill tanks if empty 
Turn on valve if off 
Clean pipes 

Clean out air vent in grav- 
ity tank 

Clean jets 

Remove dirt in pipe 
Clean float needle valve 
Drain water from carbu- 
retor 

If in generator, look under 
" Generator troubles" 

If in battery, look under 
"Battery trouble" 

Broken wire: Replace. If 
magneto is used, adjust 
breaker points. Clean all 
leads 

Wipe out distributor 

Check up induction or 
transformer coil 

Check up condenser 

If necessary remove mag- 
nets and remagnetize 

Remove plugs and clean 
Adjust spark plug gaps 
Examine for broken por- 
celain 

Replace all parts affected 
and examine for obstruc- 
tions in oil pipes and cool- 
ing system 



Note: A broken part is sometimes due to a flaw either in that parti- 
cular part, or some part affecting its operation. 



382 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



Q. 4. Name some troubles that cause loss of power and 
overheating, and give their remedy. 
A. (1) Structure troubles: 



Excessive carbon 

Exhaust manifolds or pipes 
of insufficient capacity 

Air leaks intake manifold 



Bearings (connecting rod 
and main) tight 

Crankshaft spring or jour- 
nals grooved 

Wrist pin loose, scores cyl- 
inder 

Piston worn out of round, 
binding scoring cylinder 

Piston rings worn out, 
grooves in line, losing 
spring 

Camshaft or operating gear 
sprung, bearings worn, 
gears not meshed properly 

Valve clearances too close or 
too far apart 

Valve stems worn, gummed 
or bent 

Valve stem guides worn 



Valve blowing due to burn- 
ing and warping 

Spark plugs leaking in 
threads 



Knocking or preignition 
Engine seems to drag 



Engine does not idle well, 
"pops" and "drags" at 
high speed 

Overheating due to friction. 
Engine turns hard 

Overheating due to friction. 



Loss of power, due to loss of 
compression 

Loss of compression, over- 
heating due to friction 

Loss of compression, gas 
blows by spark plug, soot 



Irregular valve action 



Loss of power and some- 
times overheating 

Hissing 



Loss of compression 



Hissing noise, loss of power 
and speed 

Hissing 



Clean 

Either do away with the 
pipes or enlarge 

Repair or replace 



Adjust by inserting shim 



Straighten in press, crocus 
or smooth up 

Replace and fasten securely 
If necessary replace cylinder 

Replace if possible, or 
smooth up 

Replace, clean grooves 



Straighten, renew bearings, 
mesh gears, properly re- 
time 

Check and readjust 



Straighten, and if necessary 
replace 

Either ream and bush or re- 
place bushing 

Reseat and regrind and set 
clearances 

Tighten, and if necessary re- 
place gasket 



AIRCRAFT ENGINE TROUBLES 



383 



2. Auxiliary troubles. 



Radiator filled with sedi- 
ment 



Water jackets and pipes 
clogged with dirt 

Water pump not working 



SYMPTOM 



Overheating radiator will be 
hot in some places and 
cool in others 

Overheating — loss of power 



Overheating and rattle 



Clean out by boiling with 
lye solution 



Clean out 



Repair shaft 



Note: Sometimes the inner rubber or fabric of the hose becomes sep- 
arated and causes an obstruction of the water passage. 



Not enough water in radi- 
ator 

Lubrication system not 
working 



Carburetor trouble 



Ignition trouble mostly 
caused by improper ad- 
vance or timing 



Radiator will boil very soon 



Overheating due to friction, 
oil temperature high, oil 
pressure too low or too 
high 



Loss of speed, overheating, 
loss of power (knock due 
to preignition) 



Fill 



Adjust oil pressure, clean 
lines, renew broken line 



Look under "Carburetor 
troubles' ' 



Retime 



Q. 5. Name some troubles that cause missing and poor 
operation, give remedy and divide under structure and 
operation. 



384 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

A. 1. Troubles that cause missing and poor operation. 



TROUBLE 



Cylinder walls scored 



Piston badly worn 

Piston rings worn, loose 
spring 

Carbon deposits on piston 
or in combustion chamber 

Valve operating gear loose 



Valve clearance too much or 
too little 



Valve springs broken or 
weak 

Valves blowing due to wear 
or burning 

Leaking intake manifold ad- 
mitting air 

Spark plugs not tight, brok- 
en or dirty 

Priming cock, loose in 
threads or jarred open 

Twisted camshaft (rare) 



Poor suction at intake mani- 
fold, oil leaks at exhaust 
valve 

(Same as above) 

(Same as above) 

Preignition (knock) 



Engine misses due to being 
out of time 

One or more cylinders miss, 
according to the number 
of valves out 

(Same as above) 



Missing and hissing sound Regrind and adjust 



Regrind or replace, fitting 
new piston 



Renew 
Renew 

Remove cylinders and clean 
out carbon 

Bush guides, renew tappets 
Readjust clearances 



Replace 



Motor will not idle. Hiss- 
ing sound 

Cylinders "cutting out" 
regularly 

Motor will not idle well 
Hissing sound 

Missing due to engine being 
out of time 



Renew gaskets and repair 
if necessary 

Clean and tighten. Renew 
if necessary 

Shut up and tighten if nec- 
essary 

Straighten if possible, if not 
renew. Retime 



Note: Some camshafts are built up and not ground from a master 
cam. Set clearance by placing each piston in position of valve 
opening. 



AIRCRAFT ENGINE TROUBLES 



385 



Carburetor trouble 



Ignition, loose wire or 
broken insulation. Igni- 
tion (if in generator or 
battery) 

Dirty distributor blocks and 
contact points 



Missing, "popping" or 
"blowing" back 

Missing 



Missing 



Adjust. See "Carburetors' 



Look up under "Battery 
and generator troubles" 



Clean with gasoline or metal 
polish, smooth points and 
clean with fine brush 



Q. 6. Name some troubles that cause knocking and noisy 
operation, giving their symptoms and remedy. Divide 
troubles under structural and auxiliaries. 

A. 1. Structural troubles. 



TROUBLE 


SYMPTOM 


REMEDY 


Engine loose on bed 


Very heavy knock or 
pounding 


Tighten bolts 


Propeller hub loose on flange 


Same as above 


Secure 


Propeller out of track 


Vibration due to propeller 
flutter 


Line up, either by use of 
shims or facing hub 


Main bearings worn, loose 
bolts 


Sharp knock 


Tighten bolts, remove shims 
or file off caps 


Connecting rod bearings 
worn; loose bolts 


Sharp knock 


Tighten bolts, remove shims 
or file off caps 


All bearings too tight 


Squeaking— engine turns 
hard 


Readjust 


Wrist pin bushing worn 


Very sharp knock 


Re-bush and if necessary 
replace pin 


Piston too loose or too tight 


Slapping noise noticed at 
low speeds, squeaking 


Refit, allowing proper clear- 
ance 


Overheating, anything caus- 
ing this will cause noisy 
operation 


Knocking due to preignition 


Remedy as directed before 


Valve operating gear, loose, 
improper clearance, etc. 


Clicking 


Remedy as directed before 



386 



AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



A. 2. Auxiliary troubles. 



TROUBLE 


SYMPTOM 


REMEDY 


Ignition spark not timed 


Knock due to preignition, 


Retime 


properly; too much ad- 


knock due to overheating, 




vance or retard 


loss of speed 




Carburetor too lean or too 


Backfire, popping, knocking 


Look under "Carburetors" 


rich 






Lubrication, anything caus- 


Knock or squeak; engine 


Be sure that there is oil 


ing overheating 


turns hard 


under proper pressure and 
that pipes are clear 


Water service blocked, 


Knock due to overheating 


As stated before 


pump not working, no 






water, radiator filled with 






sediment 







Note : Whenever a knock develops , it should be investigated immedi- 
ately, the sooner the better, for if taken in time one may prevent 
to the entire structure. 



Q. 7. Name some troubles that would cause hard starting 
or failure to start, giving their symptoms and remedy. 

A. (Note): If the engine does not start after it has been 
primed and cranked a few times, it is advisable to look for 
the trouble. Remember it is unnecessary to stand and 
crank unless the engine shows some sign of starting. 

1. Structural troubles. 



TROUBLE 


SYMPTOM 


REMEDY 


Engine turns very hard or 




Look for frozen piston or 


holds fast 




bearing, or broken part 


No compression 


Engine will turn very easy 


Look for sticking valves, 
worn rings or piston. No 
oil 


Valve improperly timed 




Retime 



AIRCRAFT EXGINE TROUBLES 



387 



2. Auxiliary troubles. 



No gasoline, lines plugged 
with dirt, valve shut off. 

Jets plugged with dirt, 
water in gasoline 



Primed too little or primed 
too much 



Tgnition 



Weak battery 



l.oose or broken wire 



Oil soaked wires causing 
short circuit 

Distributors soaked with 
moisture or dirty 



Burned out magneto wind- 
ings, poor condenser 

Spark plug points not prop- 
erty placed 



Wrong connections, i. e., 
leads to plugs out of place 



Dirty plugs 



Weak magnets (magneto) 



There will be no gasoline in 
float chamber. (If spark 
is good, failure to start is 
generally due to gasoline 
troubles) 

Popping and blowing back 



(If gasoline supply is O. K. 
and carburetor appears to 
be functioning properly, 
test ignitions 

No spark or weak spark and 
plu<rs. (No d'scharge 
shown with switch on) 

Same as above 



Same as above 



Same as above 



Same as above (arcing at 
breaker points) 

Very weak spark or no spark 
at all when plug is re- 
moved and grounded on 
engine 

Spark all right, still engine 
does not run (rare) 

Spark occurs when wire is 
removed from plug and 
grounded on cylinder 

W r eak spark or no spark at 
nil 



Turn on valve, fill tank 
Trace trouble as directed 
under "Carburetors" 



Prime or work excess fuel 
out by rotating engine 
backwards 



Look up under "Battery 
troubles" 



Check up wiring; renew 
broken wires 

Clean wires; renew if nec- 



Wipe dry with soft rag. (It 
may be necessary to re- 
move them and dry in an 
oven) 

Renew 



Readjust 



Check and place in proper 
position 



Clean plugs 



Remagnetize 



CHAPTER LV 
The Liberty Aircraft Engine 

Q. 1. Give a brief history of the Liberty engine. 

A. The Liberty motor or the United States standard air- 
craft motor was developed for use during the war with 
Germany. It is a combination of the best features of air- 
craft engines that were in use at that time, and was designed 
by a group of aircraft engine designers who gave their product 
to the government. It was originally intended to produce 
this engine in four different models of four, six, eight, and 
twelve cylinders each, but advices from the front indicated 
that engines of great horsepower were required, so the 
twelve cylinder model was standardized, and manufactured 
by a number of the large automobile manufacturing con- 
cerns. All parts are interchangeable, and it was intended to 
keep a large stock of parts on hand and replace broken or 
damaged parts instead of repairing them. 

Q. 2. Give a detailed description of the Liberty engine. 

A. It is a twelve cylinder model with the cylinders set at 
an angle of 45°, and so designed to develop either 370 or 
425 H.P. by simply changing the pistons. The motor 
developing 370 H.P. is the one used generally by the Navy, 
and is equipped with flat top pistons. The other type using 
a dome-shaped piston is used generally by the Army. The 
weight of the engine, not including radiator, propeller, fuel 
and oil tanks, is 806 pounds, the fuel consumption being 
about 30 to 34 gallons per hour, according to the engine, at 
wide open throttle. The oil consumption is about If gallons 
per hour at wide open throttle. The water pump and water 

388 



THE LIBERTY AIRCRAFT ENGINE 389 

service (not including radiator) hold about 5J gallons of 
water. The Delco system, designed especially for this 
motor, is used. It consists of a storage battery, either 
Willard or Exide type, rated at 6 volts, 9 ampere hours, a 
specialty designed 4 pole wave wound generator, two dis- 
tributor heads, a special switch and voltage regulator. The 
entire ignition system weighs but 34 pounds 6 ounces. Two 
Zenith (U.S. 52) duplex carburetors fitted with a special 
altitude compensating device are used. 

Q. 3. Describe the Liberty crankcase. 

A. It is cast of aluminum in two halves, each half holding 
one-half of the bearings, in order to obtain rigidity. It is 
held together with sixteen large studs. The thrust housing 
is designed in such a manner as to allow it to be used either 
as a tractor or a pusher. The forward portion of the lower 
half is so shaped to hold the oil pump, and the after portion 
is fitted with a drain. The two halves of the case are lapped 
and fitted together to hold oil. 

Q. 4. Describe the Liberty crankshaft. 

A. It is forged and machined from a special heat treated 
steel, and has six throws set 120° apart. It is drilled hollow 
to eliminate weight and allow oil passage and rests in seven 
main bearings. It is fitted with a propeller hub on one and 
the main driving gear (for generator, oil pump, and valve 
driving apparatus on the other). 

Q. 5. Describe the Liberty connecting rods. 

A. The connecting rods are of the blade and fork type, 
the blade rod fitting on the crankshaft, and the fork rod 
over the blade rod. They are forged and machined from 
a special heat treated steel of I beam form. 

Q. 6. Describe the Liberty piston. 



390 



A. It is of aluminum (Lynite), and so designed to carry 
the heat to the cylinder walls. It is fitted with three con- 
centric rings. The wrist pin is not held stationary in the 
piston bosses, but allowed to float back and forth. Two 
aluminum piston pin retainers are pressed into the piston on 
either side of the end of the wrist pin and prevent the pin 
from scoring the cylinder. 

Q. 7. Describe the Liberty cylinder. 

A. The barrel is forged out of steel and the valve pockets 
welded in. The intake valve is on the inboard side and 
exhaust valve on the outboard side. The entire assembly 
is machined, and then the water jackets made of Russia 
iron (in two halves) are welded in place. The cylinders are 
numbered on the edges of the base flanges. They are held 
in place with 10 studs. 

Q. 8. Describe the Liberty cooling system. 

A. Cooling water is circulated by a centrifugal pump, 
running at 1J times engine speed, and capable of pumping 
100 gallons of water per minute at full speed. The pump is 
provided with a single inlet of 2 inches outside diameter, 
and two outlets of 1J inches outside diameter. The water 
is forced in at the base of each cylinder jacket tangent to 
its outside surface which gives the water a whirling motion 
insuring uniform cooling The water outlet pipe extends 
inside the cylinder to a point close to the exhaust valve, 
which insures the proper cooling of this valve. From here 
the water is conveyed through passages cored in the intake 
header, where it assists in heating the mixture, and is cooled 
to some extent. The passages in the intake header are 
connected by two water outlet headers, the final outlet being 
2 inches outside diameter. 

Q. 9. Describe the Liberty oiling or lubrication system. 



THE LIBERTY AIRCRAFT ENGINE 391 

A . The oil for the Liberty engine is carried in two external 
tanks placed so as to act as coolers. 

Note: In navy planes they are mounted on either side of the engine 
bed. 

Oil is led from these tanks to the oil pump in the lower 
portion of the crank case through the connection on the 
right side of the pump marked "oil in." Here it is filtered 
by passing through a fine mesh screen. A gear type delivery 
pump takes the oil from the filter and passes it under a 
pressure not exceeding 50 pounds per square inch (controlled 
by a pressure regulating valve between the pump and main 
distributor pipe), through the main distributor pipe running 
the length of the crankcase. 

The oil is then forced to the main bearings through pipes 
fitted in the case and leading from the main distributor pipe. 
The crankshaft is hollow and holes are drilled to allow the 
oil to pass from the main bearings into the shaft and out on 
the crank pin to oil the connecting rods. The oil is thrown 
off of the rapidly revolving rotating end of the connecting 
rod forming a spray which oils both the cylinder w r alls and 
the wrist pin. 

Part of the oil led to the main bearings at the propeller 
end of the motor passes around this bearing and up through 
pipes to the propeller end of the camshaft housing, then 
through a passage around the bearing to a hole in the bearing. 
The camshaft is drilled to receive this oil and being hollow 
it carries it to each camshaft bearing. The excess oil working 
out of the bearings is held in a small reservoir at a depth of 
about J inch. The revolving cams dip this oil and splash 
it over the rollers and into pockets in the rocker lever shafts, 
which are hollow, and convey it to the rocker shaft bearing. 
That portion of the oil left finds its way to the gear end of the 
camshaft housings, flowing over the gears and down the 



392 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

drive shaft housing to a chamber just above the oil pump. 
The oil thrown off into the crankcase is also collected in this 
chamber when the engine is inclined, so that the propeller 
end is high. Another chamber is provided at the propeller 
end of the engine for the oil that drains to it when the 
propeller end of the engine is low. Another pump and oil 
return pump situated above the oil delivery pump, and driven 
by the same shaft, collects the oil through two inlets from 
these two chambers, and sends it to the two reservoirs or 
external tanks, through the connection on the left side of 
the engine marked "oil out." 

Q. 10. Describe the Liberty camshaft. 

A. The valves are operated by two overhead camshafts 
running in a cast aluminum housing. The camshaft is 
forged and machined from a special heat treated steel, the 
cams being forged integral with the shaft and ground from 
a master cam. 

Q. 11. Describe the Liberty carburetor. 

A. The Zenith Model U.S. 52 carburetor operating on the 
principle mentioned under carburetors is used on the Liberty 
engine. It is a duplex carburetor, which is equivalent to 
two carburetors, and as two of these are used, we have four 
mixing chambers, each one supplying three cylinders, and 
but two float chambers. The most important addition in 
this make of carburetor for the Liberty engine is the altitude 
adjusting device. The float chamber is open to the air 
through two screened air inlets, and the idling or com- 
pensating well is in open communication with the float 
chamber. There is also a passage connecting the float 
chamber and the mixing chamber, in which a manually 
operated stop cock is fitted, connected to an operating 
lever in the pilot's seat. 



THE LIBERTY AIRCRAFT ENGINE 393 

On the ground and at low altitudes this valve is closed, 
the carburetor functioning as described under carburetors, 
for the float chamber is open to the atmosphere. At altitudes 
above 6000 feet, this valve is opened and the suction in the 
mixing chamber creates a vacuum in the float chamber, 
through the medium of the connecting passage, thereby 
reducing the amount of fuel flowing out of this chamber. 
The reason for this is that the density of air decreases as 
the altitude increases. 

Q. 12. Give a general description of the Liberty ignition 
system. 

A. Ignition is supplied by a special Delco generator 
batteiy unit. Below a speed of 650 R.P.M. the current 
is drawn from the battery described under "Batteries;" 
above a speed of 650 R.P.M., the current is drawn from the 
generator. The output of the generator is regulated by a 
specially designed voltage regulator. 

The regulator consists of an iron core on which are wound 
three coils, one magnetizing the core, another a reverse coil 
demagnetizing it, and the third a non-inductive resistance 
coil. By adjusting the tension of the spring the output of 
the generator is regulated. The regulation consists of 
weakening the field strength or the number of magnetic 
lines of force cut by the armature in the generator. A 
duplex switch is used and when either one of the switches 
is on, the current is drawn from the battery. When both 
switches are on, the current is drawn from the generator, 
the batteiy floating on the line. An ammeter is incorporated 
in the switch box and should show a 4 ampere charge while 
flying. 

A Bakelite distributor head is fastened to both camshafts 
on the forward end of the engine. There are two main 
breakers and one auxiliary breaker in the line. The auxiliary 
breaker prevents backfiring. 



394 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

The condenser and transformer coil are contained in the 
distributor head. The left distributor fires the plugs on the 
propeller end of the cylinder, and the right distributor fires 
the plugs on the gear end of the cylinder. 

Q. 13. How would you disassemble, overhaul, and reas- 
semble a Liberty motor? Give each step. 
A . Order of tear down — Liberty motor : 

DUAL IGNITION SYSTEM 

a. Each distributor fires one plug in each cylinder through- 
out entire cylinders. 

b. Right distributor fires plug on gear side of cylinder 
while the left fires propeller side. 

c. Disconnect high tension conduit which is attached to 
outlet water header by cap screws with no washers. 

d. Remove the 12 insulated wires fastened to spark plugs, 
being careful not to spring bell-clips. Rubber ferrules on 
end, must be in perfect condition to assure perfect insulation. 

e. Remove distributor heads held by wire clips along with 
the conduit. Care should be taken to bind the brushes 
with a rag or rubber band to prevent breakage. 

CAMSHAFT HOUSING ASSEMBLIES 

a. Remove distributor tie-rods found in upper holes with 
boss down. 

b. With snapper wrench remove collars on camshaft 
housings. A felt washer should be inserted in each collar to 
prevent oil leakage. 

c. Loosen castle nuts on the 12 studs of each camshaft 
housing; plain washers are found under each nut. 

d. Disconnect oil pipes leading to camshaft before remov- 
ing camshaft assemblies which are marked either right or 
left. 



THE LIBERTY AIRCRAFT ENGINE 395 

e. Male splines on jack-shaft marked by a groove in one 
tooth. 

/. Female spline carries two niches on collar. Both 
splines must coincide for timing. 

g. Remove camshaft assembly by raising assembly 
squarely off of cylinders. 

GENERATOR 

a. Held by three castle nuts on studs. Plain washers. 
An oil paper gasket is found between generator pad and seat. 

b. Only one bearing in generator. 

c. Power connections not marked. 

d. Splines must fit closely to prevent any back lash (come 
out rather hard) . 

CARBURETOR 

a. Unfasten carburetor tie-rod. Purpose of tie-rod to 
make carburetors work simultaneously. 

b. Watch taper pins that lock tie-rod. 

c. Be careful of pins, easily lost. 

d. Two copper asbestos washers separate each carburetor 
from manifold. 

e. Although interchangeable, make each carburetor pro- 
peller end and gear end. 

/. Each carburetor held by two anchor bolts with plain 
washers fastened to hot water intake head. 

g. Remove water outlet headers before removing car- 
buretors. 

HOT WATER INTAKE HEADER 

a. Held by four castle nuts with washers at each end 
having also two oil paper gaskets. 

b. This part, with carburetor, remove practically at the 
same time, holding one in each hand. 



396 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

MANIFOLD OR INTAKE HEADERS 

a. Four in number, each held by six studs, castle nuts 
and washers, paper gaskets between each. 

b. Each manifold stamped on exhaust flange-propeller end 
right or left and gear end right or left as the case may be. 

c. Remove that manifold with smallest bearing surface 
first, found here to be right side. 

d. Inspect manifold for loose cores which rattle. 

WATER SYSTEM 

a. Remove both outlet water pipes from pump. Right 
side is larger than left. 

b. Remove inlet water headers; both pipes are inter- 
changeable (hose bands). 

c. Remove outlet water pipes of cylinders; loosen all hose 
bands attached to cylinder. 

d. Three flanges attached to each manifold and held there 
by two cap screws through each flange having drilled heads. 
(Paper gaskets between manifold and each flange.) 

e. Centrifugal pump — water pump — held by four studs 
with castle nuts, paper gaskets separate pump pad and seat. 

/. Pump intake points to the left plugged hole found at 
the bottom. 

BREATHERS (CRANKCASE) 

a. Two crank case breathers on right side of engine, held 
by two nuts with paper gaskets. 

b. Screened baffle at hole in case to prevent oil splashing 
out. 

c. Wire strainer cloth under cap of each breather for 
pouring oil. 



THE LIBERTY AIRCRAFT ENGINE 397 

BREATHERS (GEAR END) 

a. Held by two studs, washers and castle nuts, has paper 
gasket between, also baffle plate screen. 

b. On the propeller end the three way distributor for oil 
is fastened by two castle nuts, washers and has an oil paper 
gasket. 

CYLINDERS (TWELVE) 

a. Start from gear or propeller end and remove flange nuts 
between each cylinder. Six other castle nuts serve to hold 
flange to cylinder pad. 

b. Paper gaskets between cylinder pads and flanges are 
cut to cover three cylinders. 

c. Remove one spark plug before pulling cylinder off piston 
to relieve vacuum. 

d. Be sure cylinders are marked on flange below exhaust 
port. 

PISTONS 

a. Bind studs at base of cylinder pad to prevent scratching 
of pistons. 

b. With pliers remove wire piston pin retainers. 

c. Drive out piston with brass plug, pounding it gently. 

d. Piston pin should only be driven far enough to clear 
pin housing. 

e. Each piston is marked right or left and its number 
position. 

/. Allow rings in grooves to remain untouched. 

g. Rings are common split type with two right and one left. 
The splits being set at 180 degrees apart. 

h. While removing piston pin hold piston firmly so as not 
to throw connecting rods out of line. 

i. Be sure all pistons are marked on relieved surface 
toward gear end. 



398 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

GENERATOR AND CAMSHAFT ASSEMBLIES 

a. Remove gear case cap held by six cap screws drilled for 
wiring, no washers. 

b. Remove jack shaft assemblies held by four stud castle 
nuts. 

c. Should have a paper gasket between crankcase and pad. 

d. Each shaft marked right or left on the beveled gear. 

e. Ball race retainers in assembly. 

/. These shafts must be removed before generator shaft, 
as gears of former prevent removal of latter. 

REMOVE GENERATOR DRIVE SHAFT 

a. Duty; to drive generator and two jack shafts. 

b. Construction; with key-way in shaft for jack shaft 
gear, and two spacing sleeves to hold it where it belongs. 

c. Bevel gear has twenty-two teeth. 

TIMING 

a. When 1 and 6 left are 10 degrees past dead center, 
splines should be placed in line with center of cylinder. 

REMOVAL OF LOWER CRANK CASE 

a. Loosen fourteen nuts on anchor bolts, a plain washer 
is found beneath each. 

b. Turn crank case over allowing anchor flange to rest on 
wooden blocks mounted on frame. 

c Remove two through bolts on end of each case. Also 
two anchor bolt nuts are found at propeller end and removed. 
Remove oil pump held by ten castle nuts with washers. A 
paper gasket is found between. 

d. Remove fifty hexagon head bolts holding upper and 
lower crank cases together. 

e. Lift off lower part of crank case. 



THE LIBERTY AIRCRAFT ENGINE 399 

REMOVAL OF SPOOL GEAR 

a. Loosen set screw which holds assembly in place. 

b. With case upright drive assembly through. 

c. Upon measuring it will be found to be tapered .0007 
inch over a distance of 2\ inches. 

FORK AND PLAIN END CONNECTING RODS 

a. End play of connecting rods allowed .005 inch found to 
be as great as .016 inch. 

b. Babbit metal bearing surface on fork rods bronze on 
plain end. 

REASON 

c. Plain end rod was removed first by turning shaft to 
allow it to let go easily upon removing nuts. 

d. Forked rods followed, care being taken to place both 
halves of bearing surface as they originally were. 

UPPER HALF CRANKCASE 

a. Inspect bearing surfaces — high spots show up bright. 
(Should be a lead color throughout.) 

b. Watch studs for loosening up. 

c. Care should be taken to find any cracks or sand holes. 

CRANKSHAFT INSPECTION 

a. Inspect crank pins and main bearings for any scratches 
or rough spots. Crocus cloth will remove any slight 
scratches. 

b. Teeth of driving gear on gear flanges should be perfect 
and not chewed up. Prick punched 12 degrees 30 minutes 
past center for timing purposes. 



400 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

CAMSHAFT ASSEMBLY 

a. Remove the six plates holding rocker arms in place, held 
by three hex. bolts and plain washers. 

b. Withdraw bearing retainers which are set screws used 
to hold bearings in place. 

c. Remove oil cap on gear end with a spanner wrench. 

d. Remove 6 hex. nuts which hold distributor flange in 
place. 

e. Withdraw camshaft with bearing attached. 

/. Split bearing surface held by set screws — bearings are 
aluminum except at gear end, which is a bronze bearing. 

CRANKCASE (UPPER HALF) 

a. Place crankcase in inverted position. 

b. Clean all bearing surfaces. 

CRANKSHAFT 

a. Clean all main and pin bearings. 

b. Shaft, when seated, should have no end play. 

CONNECTING RODS 

a. Female connecting rods go to right cylinders in order 
indicated on "I" section. 

b. Stamped surface should appear on gear side. 

c. Numerals on bearing retainers, both halves, should 
correspond. 

d. For male rods move shaft until rod enters female freely. 

e. Position number on "I" section faces gear end. 

/. Crank pin end of rod numbered, both halves of same 
should correspond. 



THE LIBERTY AIRCRAFT ENGINE 401 

BOLT CASES TOGETHER 

a. Two through bolts on propeller and gear end drop into 
place and fastened. 

b. Fifty hexagon anchor bolts placed and tightened to hold 
upper and lower cases together. 

TURN CASE OVER 

a. Tie connecting rods to stud with rags and invert. 

b. Place hexagon nuts on the fourteen through bolts 
securing upper and lower crankcases. 

MOUNT OIL PUMP 

a. Fasten by 10 nuts, plain washers. 

b. Paper gaskets between pad and flange. 

c. Strainer in oil pump cap fastened by 3 nuts and plain 
washers, no paper gaskets found. 

GENERATOR DRIVE SHAFT ASSEMBLY 

a. Placed in position — fasten flange by three nuts and plain 
washers, no paper gaskets. 

JACK SHAFT ASSEMBLY 

a. Marked right and left on beveled gear — place as 
indicated. 

b. When No. 1 and No. 6 cylinders, left side, are 10 degrees 
past dead center. 

c. When No. 1 and No. 6 right are 10 degrees past dead 
center, marks on female spline should be on line with dead 
center. 



402 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 



GEAR END PLATE 



a. Secured by six hexagon head set screws, whose heads 
are drilled for wiring. 



JACK SHAFT FLANGES 



a. Held by four hexagon nuts — no washers. 

b. Threaded for camshaft collars. 



WATER PUMP 

a. Bolt water pump on lower crankcase with four nuts 
and plain washers. 

b. Plugged hole at bottom. 

c. Inlet from radiator faces to left. 

PISTONS 

a. Each piston is cleaned thoroughly and placed in position 
as stamped on side. 

b. Piston pin is driven gently through piston and when in 
place wire retainers are set in grooves to hold pin in place. 

c. The retaining clamps held in pliers — when compressed 
are dropped in groove. 

CYLINDERS 

a. Cylinder walls carefully cleaned. 

b. Rings of piston compressed with hands to allow cylinder 
to pass over. 

c. Cylinder held in place by nuts applied to skirt flange. 



THE LIBERTY AIRCRAFT ENGINE 403 

BREATHERS 

a. Crankcase breathers. 

b. Held by two stud nuts. Paper gaskets between. 

c. Make certain wire strainer is held within crankcase 
wall and that strainer cloth is O.K. beneath cover. 

d. Three-way oil pass on propeller end held by two nuts 
on studs. Paper gasket is used. 

MANIFOLDS 

a. Left manifold held in position with nuts tightened, 
while right manifold is wedged into place. 

b. Left manifold has less bearing contact and therefore 
offers less obstruction to right manifold which has a greater 
bearing surface. 

HOT WATER HEADERS 

a. Secured to manifolds first before final tightening of 
manifold flanges. 

b. This done in order to prevent any possible water 
leakage 

CARBURETORS 

a. Carburetors designed rear and propeller end. 

b. Held in place by two bolts through hot water header 
and hang suspended between cylinders. 

Q. 14. How would you time a Liberty engine? Give all 
steps in detail. 

A. 1. If the timing disc is not already mounted on the 
propeller hub, install it in such a manner that the dowel in 
the propeller hub flange enters the dowel hole in the disc. 
It may be clamped in this position by means of two bolts 
through the propeller hub bolt holes. 



404 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

2. Remove the spark plug from the propeller side of No. 
6 L cylinder. 

3. Insert a pencil or scale through the spark plug hole 
and turn the engine over until the piston on its up stroke 
touches the pencil and causes it to ride up. Continue to turn 
the engine over slowly until the piston as indicated by the 
travel of the pencil stops moving upward and is just about 
to start down. This will be approximately the top dead 
center. 

4. Allow the crankshaft to remain in this position tem- 
porarily and clamp the timing pointers, which will be found 
in the tool kit, under the special cylinder base flange nuts, 
so that the pointers extend over the edge of the timing disc. 

5. With the end of the pencil resting on the top of the 
piston make a mark with a knife blade about one-half inch 
above the edge of the spark plug hole. 

6. Turn the engine over in a forward direction until the 
pencil has moved down so that the mark is even with the 
top edge of the hole, and with a piece of chalk or a pencil 
mark the disc in line with one of the pointers. 

7. Turn the engine backward until the pencil has moved 
up and down to the point where the mark is again even with 
the top of the spark plug hole, and mark the disc in line with 
the pointer. 

8. With a pair of dividers find the point midway between 
the two marks on the disc. This point will indicate the exact 
dead center of No. 1 and No. 6 cranks and should be marked 
with chalk or pencil. 

9. Turn the engine over until this dead center mark is in 
line with the pointer. Allow the crankshaft to remain in 
this position and, 

10. Reset the pointers so that they come in line with the 
dead center marks stamped on the disc. 



THE LIBERTY AIRCRAFT ENGINE 405 

11. Turn the engine over in the direction of rotation 
through ten degrees as indicated by the scale on the disc. 
The crankshaft is now set on the neutral point of No. 6 left 
cylinder and the firing point — spark retarded of No. 1 left 
cylinder. "Neutral point" is the point ten degrees past 
the top dead center which marks the beginning and end of 
the cycle of operations. The exhaust valve closes and the 
inlet valve opens at this point. 

Mount the generator drive shaft assembly, being careful 
that the gasket is in place and a sufficient number of shims 
(.002 inch thick) to insure proper mesh of the generator 
drive shaft lower gear with the crankshaft gear. These gears 
should have a minimum back lash of 0.005 inch and a 
maximum of 0.010 inch. 

Mount the two camshaft drive shafts, meshing the gears 
in such a manner that the mark on the splined couplings is 
"fore" and "aft" or parallel with the center line of the engine. 

Now mount the camshaft housing assemblies. 

If it was not found necessary to replace either the camshaft 
or gear, be sure that the marked teeth on both gear and 
pinion are in line. This should bring the mark on the 
splined end of the drive shaft "fore and aft." 

The assemblies may now be set in place with the splined 
coupling marks in line. 

Note: All marks for both right and left cylinders are located with 
No. 1-6 cranks ten degrees past left dead center. 

Complete the installation of these assemblies by replacing 
the washers and the nuts and properly cotter pinning them. 

Slip the felt washers into place and tighten up the stuffing 
boxes. 

Test the gap between all tappets and the valves which they 
operate. The tappet gap for each cylinder should be 



406 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

checked when that cylinder is on the firing point. The 
firing point of No. 1 cylinder is the neutral point of No. 6 
on the same side. The firing point of No. 2 is the neutral 
point of No. 5. The firing point of No. 3 is the neutral 
joint of No. 4. The firing point of No. 4 is the neutral 
point of No. 3. The firing point of No. 5 is the neutral 
point of No. 2. The firing point of No. 6 is the neutral 
point of No. 1. It will be noticed that the sum of the 
numbers of these pairs of cylinders is always seven. For 
example — to find the firing points of No. 4 cylinder, turn 
the engine over, meanwhile watching the No. 3 exhaust 
valve. When this valve has just closed and before No. 3 
inlet valve has opened, the neutral point of No. 3 cylinder 
will have been reached. This will be the firing point of 
No. 4. With the engine cold the clearance between the inlet 
valve tappets and the valve stems should be 0.014 to 0.016. 
The clearance between the exhaust valve tappets and valve 
stems should be 0.019 to 0.021. This clearance should be 
adjusted by adding or taking out shims under the tappet 
head. These shims are made in varying thicknesses, the 
thick shim being 0.015 inch thick, the medium shim being 
0.008 inch, and the thin shim being 0.003 inch. The com- 
bination of these shims will permit of a very accurate adjust- 
ment of the gap. Be sure that the shims are properly placed 
and that the nuts on the tappets are tightly drawn up and 
cottered. 

If it was found necessary to replace either the camshaft or 
the camshaft gear, proceed as follows: 

1. With No. 1-6 crank set ten degrees past the left dead 
center, the marked splines on the camshaft drive shaft set 
"fore and aft," the marked splines on the upper camshaft 
drive shaft in line with them, the marked tooth on the upper 
camshaft drive shaft gear should be toward the observer 
and on the center line of the cylinders. 



THE LIBERTY AIRCRAFT ENGINE 407 

2. Without moving any of this assembly rotate the left 
camshaft in a clockwise direction until the No. 6 exhaust 
valve is just closed and the inlet valve is just about to open. 

3. Now mesh the camshaft gear in such a manner that the 
teeth and the flange bolt-holes will line up perfectly. 

The camshaft gear has 48 teeth and is bolted to the flange 
by means of seven bolts. This will permit an adjustment of 
one-seventh of one tooth space or two and one-seventh 
degrees crankshaft travel. 

4. Tighten up two of the camshaft gear bolts and check 
the tappet clearance on all left cylinders. 

5. Now check the opening and closing of the exhaust and 
inlet valves. If it is found that the valves are late in opening 
and closing, the number of degrees should be noted and the 
camshaft gear moved one or more holes in the direction of 
rotation without moving the camshaft drive shaft or the 
camshaft. Remember that for each hole move forward, the 
camshaft is advanced two and one-seventh degrees of crank 
shaft rotation. If the valves are found to open early, set 
the camshaft gear backward one or more holes. 

Always check valve timing by turning engine in forward 
direction of rotation so as to take up all back lash in gears 
and lost motion in couplings. 

After the gear has been properly located, set the left dis- 
tributor driving flange over the bolts in such a position that 
the marked notch is in line with the marked tooth on the 
drive pinion. 

Now tighten up and cotter pin the bolts and mark the 
gear in line with marked tooth on the drive pinion. 

To set the right camshaft, turn the engine over in the 
direction of rotation through 45 degrees or until the No. 1 
crank is ten degrees past the right dead center. With the 
crankshaft in this position turn the camshaft over in a 



408 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

clockwise direction until the No. 1 exhaust valve is just 
closed and the inlet valve is just about to open. Locate the 
gear in the same manner as in setting the left camshaft. 

Before mounting the right distributor driving flange, turn 
the crank shaft back through 45 degrees or to its original 
position and set the distributor drive flange so that the 
marked notch comes in line with the marked tooth on the 
drive pinion, or in other words, in line with the center line 
of the right cylinders. 

Now tighten up the camshaft gear bolts and cotter pin as 
before. 

Set the two distributor assemblies in place, being careful 
to get them on the proper housings right and left. 

These distributors are marked R and L on the outside 
surface of the spark control arms. They should be fastened 
temporarily by means of two bolts, each in such a position 
that the notch on the distributor base flange coincides with 
the notch on the camshaft housing flange. 

If it has been found necessary to replace either the cam- 
shaft housing or the distributor head, and the new parts do 
not carry these identifying notches, the distributor should be 
so set that with the spark retarded the center line of the 
cylinders will be midway between 1 L and 6 R terminals. 

1. Set the engine on the firing point, spark retarded, 
No. 1 L cylinder, in other words, the neutral point of No. 
6L. 

2. Swing the timing lever on the distributor to the full 
retarded position or as far in a clockwise direction as is 
possible. 

3. Loosen the bolts sufficiently so that the distributor base 
flange can be rotated on the slotted holes. 

4. Connect battery and electric light across the dis- 
tributor terminals, and rotate the distributor base flange 



THE LIBERTY AIRCRAFT ENGINE 409 

in a counter clockwise direction until the light just goes 
out. Tighten the bolts with the distributor in this position 
and complete the installation of the bolts. 

5. Without changing the position of the crankshaft install 
and set the right hand distributor in a similar manner. 

6. The accuracy of the timing should now be checked up 
by rotating the crankshaft backward 15 or 20 degrees, then 
forward very slowly, meanwhile watching the electric lights. 
They should both go out at the same time within a limit of 
one and one-half degrees on the timing disc. If the pocket 
flashlight is used instead of the two electric lights 'and 
battery, each distributor head will have to be checked 
separately and the time of the break noted according to the 
timing disc. 

7. Install the cross reach and adjust it so that both 
distributor heads will be fully retarded. Check the syn- 
chronization of the two distributor heads with spark lever 
in advanced position also. 

8. Install the high tension cable tube and cable assembly, 
fastening it by means of the screws to the intake headers. 

9. Wire the heads of all these screws so that they will 
not loosen up. 

Caution: Care should be exercised in placing the distributor head 
assembly on the distributor to keep from breaking the rotor brush. 
It can best be done by putting the distributor head assembly over the 
two studs, and slightly rocking it back and forth with the rotor in the 
right angle position to the center line of the two studs. This will 
gradually work the brush into the rotor and allow the distributor 
head to slip down into place. 

Q. 15. What precaution must be taken when testing a 
Liberty motor? 

A. If the engine being tested is designed for use in high 
altitudes, it is equipped with dome top pistons. It should 
not be run on stand with the throttle more than one-half 



410 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

to two-thirds open. With these dome pistons the com- 
pression is excessive at low altitudes, and if run at open 
throttle, a break down will result. Engines fitted with flat 
top low compression pistons may be run on the stand with 
wide open throttle. 



CHAPTER LVI 
Hispano-Suiza Engine 

Q. 1. Give a brief description of the Hispano-Suiza 
engine. 

A. The model "A" Hispano, used for N-9 training sea- 
planes in the navy, develops 150 H.P. at 1450 R.P.M. at 
sea level. It is V type water cooled 4 cycle engine; cylinders 
120 mm. (4.72 inches) bore by 130 mm. (5.11 inches) stroke, 
set at an angle of 90 degrees. It is equipped with the 
Zenith carburetor and two Dixie No. 800 magnetos, and has 
a separate hand starting magneto. 

The engine without propeller, fuel, oil, water and tanks 
weighs 470 pounds. 

The firing order is 1 L— 4R, 2 L— 3R, 4 L— 1R, 3 L— 2R. 
This engine uses about 15 gallons of gasoline per hour, at 
full speed, and f gallon of oil also at full speed. The water 
pump is capable of delivering about 26| gallons per minute 
at wide open throttle. The valve clearance is 2 mm. or 
0.078 inches. 

Q. 2. Describe the Hispano-Suiza cylinder block and 
cylinders. 

A . The individual cylinders are steel forging, heat treated, 
machined and threaded on the outside. These sleeves are 
flanged at the bottom and closed at the top, this surface 
being flat, providing for the two valve seats. The cylinders 
or sleeves are screwed into a cast aluminum block which 
forms the water jackets, valve ports, intake and exhaust 
passage. 

411 



412 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Q. 3. Describe the Hispano-Suiza piston. 

A. The piston is of cast aluminum f inch thick at the 
head. The sides taper from f inch at the top to J-inch 
thickness at the bottom. This construction insures a rapid 
disposition of the heat. There are four narrow rings in 
two grooves at the top. There is one oil ring near the 
bottom with a relief just below it. The wrist pins or piston 
pins are hollow and made of case-hardened alloy steel. 
They are allowed to float in both sides of the piston and 
upper end of the connecting rod, but are kept from scoring 
the cylinders by a piston pin lock ring. 

Q. 4. Describe the Hispano-Suiza connecting rods. 

A. They are made of heat treated steel, tubular in shape. 
One rod is forked and is fitted to the crank pin; the other 
a blade rod is fitted on to the forked rod. Both of these 
rods are provided with bronze bushings at the upper end. 

Q. 5. Describe the Hispano-Suiza crank shaft. 

A. It is of the 4 throw type, throws spaced equally 180 
degrees apart. It is made of chrome nickel steel machined 
all over, and is bored hollow for lightness and to allow 
oil passage. The shaft rests in four plain main bearings, 
and an annular ball bearing at the gear end. There is a 
thrust bearing at the propeller end suitable for either a 
tractor or pusher. 

Q. 6. Describe the Hispano-Suiza crank case. 

A. The crankcase is of cast aluminum, made in two halves, 
each half holding one half of the main bearing. The lower 
half is of very deep section, thus providing an oil reservoir 
and at the same time stiffening the engine. 

Q. 7. Describe the Hispano-Suiza cam shaft. 



HISPANO-SUIZA ENGINE 413 

A. The camshafts are hollow and supported by three 
main bearings. They are driven by two sets of bevel gears, 
and two vertical shafts from the crankshaft at one half 
times its speed. These vertical shafts are fitted with screw 
driver joints in order that the cylinder assembly may 
be removed easily. The camshafts and valve stem heads 
are all enclosed in an oil tight aluminum removable housing. 
The valve housing is fitted with an air pressure pump, the 
piston of which is operated by one of the cams. 

Q. 8. Describe the Hispano-Suiza valve gear. 

A. The valves are set vertically in the cylinders along 
the center of each block, and are directly operated by a 
single camshaft. They are made of Tungsten steel with 
large hollow stems working in cast iron bushings, provided 
at the upper end with case hardened flat headed adjusting 
screws or discs, upon which the cams operate. Two springs 
are used, either one strong enough to close the valve if the 
other breaks. The clearance adjustment between the 
adjusting screws and cams is obtained by the use of serrated 
washers. These washers are pressed upward by springs and 
hold the adjusting screw in place while they permit easy 
turning by means of a special wrench, which angularly dis- 
places the adjusting screws in the stems of the valves. The 
spring retainer washer is held in place angularly by means of 
tenons which engage slots in the stem. Nevertheless, the 
whole assembly can slide freely lengthwise. The valve 
spring holds the spring retainer to the adjustment disc, the 
rim of which is arranged with small indentations. 

Q. 9. Describe the Hispano-Suiza lubrication system. 

A. The oiling system of the Hispano is known as a 
positive force or pressure system. A sliding vane eccentric 
pump mounted vertically and directly below the gear end 



414 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

of the camshaft in the lower half of the crankcase, is driven 
by the same gear that drives the camshaft driving shafts 
at 1.2 times engine speed. This pump forces the oil through 
a filter in the lower half of the crankcase, and then through 
steel tubes cast in the crankcase to 3 of the main bearings 
to the hollow crankshaft to crank pin oiling both connecting 
rods. The spray thrown off of these rapidly revolving rods 
oil the cylinder wall, piston pin and piston. The fourth 
or front main bearing has an oil lead which takes care 
of the lubrication of the main bearing, and in addition to this 
has a by pass around the outside of the bearing which 
carries the oil to two tubes running up the front end of the 
cylinder blocks. This tube carries oil to lubricate camshaft 
and bearings, valve tappets and stems, vertical shafts and 
bearings, and the driving gear. The oil is forced into the 
front end of the hollow camshaft, and out through holes 
oiling all the parts within the upper housing, and then 
down through the vertical shaft housing and back to the 
sump. 

Q. 10. Describe briefly the disassembly, repair and 
assembly of an Hispano-Suiza engine. 

A. All navy aircraft engines must be torn down, checked 
and if necessary repaired after every 75 hours flight. 

1. The motor is fitted to the overhaul stand and torn 
down as follows: 

a. Remove ignition wires and distributor blocks intact. 

b. Remove magnetos marking their position. 

c. Remove camshaft housing and camshaft, marking 
position on gears. 

d. Remove all exterior oil connections, gear housings, 
and cylinder studs. 

e. Remove all manifolds and carburetor. 
/. Remove cylinders. 



HISPANO-SUIZA ENGINE 415 

g. Remove piston pin retainer, piston pin and piston. 

2. Turn engine on stand 180 degrees or upside down. 

a. Remove lower half of crankcase. 

b. Remove crankshaft, placing on a separate stand. 

c. Remove connecting rods from crankshaft. 

3. Place cylinders on bench. 

a. Remove valves and regrind. 

4. Place sump on bench. 

a. Remove water pump. 

b. Remove oil pump. 

c. Remove oil filter. 

d. Remove oil pressure relief valve. 

5. Inspect all parts of the disassembled engine, repair, 
or replace such parts that are worn or defective, weigh parts, 
and reassemble by starting the last operation of disassembly 
first, and so on. 

Q. 11. How would you time an Hispano-Suiza engine? 
A. 1. Secure degree plate on crankshaft. 

2. Revolve until upper dead center of L No. 1 cylinder 
is found. 

3. Turn shaft until degree plate shows piston to be 10 
degrees past upper dead center in the direction of rotation. 

4. At this point attach camshaft and mesh gear so that 
inlet valve is just opening and exhaust just closes. (Note 
valve clearance must be 2 mm. or 0.078 inches). 

5. Rotate the shaft 90 degrees further in the direction of 
rotation and set No. 4 R cylinder cams the same as No. 1. 

6. Set magnetos to break on firing cylinder 20 degrees 
20 minutes before top dead center. 

Q. 12. What precaution must be taken when operating 
Hispano-Suiza engines? 

A. The valves run hot in these engines, and must be 



416 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

watched constantly. If there is a sign of valve leaking, the 
valves should be reground immediately. In flight the 
motor should not be accelerated too quickly or idled too 
often, for this has a bad effect on the valves. 

Q. 1. Describe briefly the Union aircraft engine. 

A. This engine is used for lighter-than-air work on 
account of its power at low speed, endurance, and ability 
to idle well. It is of six cylinders in line, firing order L.H. 
engine 1, 4, 2, 6, 3, 5, — R.H. engine, 1, 5, 3, 6, 2, 4. It is 
equipped with two Zenith carburetors L B. jet 140, com- 
pensator 165, well 70, choke 31 (setting). Ignition equip- 
ment, two Dixie No. 612 magnetos, Bethlehem aviation 
spark plugs (metric). Lubrication system is force feed from 
an external tank mounted below the sump. Water cir- 
culation by centrifugal pump, capacity of which is 30 
gallons per minute open throttle. Maximum speed 1400 
R.P.M. 

TOP OVERHAUL OF ENGINES AFTER STORAGE 

All engines that have been in storage or unused in machines 
for more than three months since previous running, as 
recorded in the log book, should be subjected to top overhaul 
before being passed by the ground engineer for flight. The 
internal condition of the engine should be carefully examined 
for signs of corrosion, particular attention being paid to 
cylinder bores and all ball and roller bearings. 

In addition to the usual precautions taken after top 
overhaul to ensure that all parts of the engine, including 
ignition and carburetor systems, function correctly, special 
attention should be given to the flushing of all oilways — 
flushing, cleansing, adjustment, refilling, etc., of lubricators, 
filters, etc. 



CHAPTER LVII 



.ROUTINE INSPECTIONS 



Q. 1. What routine inspections should be carried out by 
aircraft engine mechanics? 
A. They are as follows: 

I. Daily inspection. 

Note: Aircraft should be moved either to the run way or to a suit- 
able place on the beach for testing, and the castors of the truck 
blocked. 

a. Inspect all visible bolts and nuts. 

1. See that they are properly drawn up 
and securely locked. 

b. Test engine for internal trouble. 

1. Turn propeller by hand, noting the 

following : 

a. Listen for piston slap. 

b. Listen for excessive gear lash or 

clearance: 

c. Listen for any loose bearings. 

2. If possible move propeller up and down. 

Note: If thrust bearing is loose in housing, it can be heard. 

c. Inspect propeller mounting. 

1. See that hub flange bolts are drawn 

up and securely locked. 

2. See that the retaining nut and lock 

are drawn up tight, and be sure 
that the tongue of the lock wire 
passes through both. 

3. Check pitch and track of propeller. 

417 



418 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

d. Inspect throttle and spark controls. 

1. See that throttle control of carburetor 

synchronizes. 

2. See that throttle control at pilot's 

seat permits full throttle opening. 

3. See that the spark control at pilot's 

seat permits full range of retard 
and advance. 

e. Inspect all electrical connections and igni- 

tion units. 

1 . See that all wire terminals are properly 

soldered, clear, and firmly attached 
to the distributors, generator, bat- 
tery, switch and voltage regulator. 

2. Wipe all wires, and clean all terminals. 

3. See that all wires are supported at the 

proper intervals, and in such manner 
that the insulation will not be 
abraded. 

4. Check distributors, see that rotor 

path is clean and that the breaker 
points are functioning properly. 
/. Inspect all gasoline tanks and supply lines. 

1. See that tanks are full. 

2. Inspect all tanks for leaks. 

3. Inspect all lines for leaks. 

4. Inspect the sediment trap for leaks. 
g. Check cooling system carefully. 

1. See that the radiator is full of water. 

2. Inspect pump for leaks, particularly 

the packing gland. 

3. Inspect all water service piping for 

leaks, particularly all hose con- 
nections. 

4. Inspect all jackets for leakage par- 

ticularly around exhaust valve. 



ROUTINE INSPECTIONS 419 

h. Inspect lubrication system. 

1. See that both tanks (Liberty engine) 

have sufficient quantity of oil. 

2. Inspect all oil piping for leakage, par- 

ticularly hose connections. 
i. Start engine noting the following: 

1. Speed in R.P.M. full throttle. 

2. Water temperature (not to exceed 

190° F.). 

3. Oil pressure. 

4. Oil temperature. 

5. (Liberty engine) cut each switch in 

order to ascertain whether or not 
each distributor is functioning. 
II. Weekly inspection. 

a. This should include the above, and in 
addition the following: 

1. Check valve clearances. 

2. Check compression of each cylinder, 

by turning engine over with pro- 
peller. 

3. Check friction of each cylinder by 

turning engine over with propeller. 

4. Inspect all spark plugs; remove and 

clean them. 

III. Before flight. 

a. Check spark and throttle controls. 

b. Inspect wiring and switches. 

c. Inspect fuel, oil and water supply. 

d. Inspect all pipes for leakage. 

IV. After flight. 

a. Same inspections as Before Flight, and in 
addition the following: 

1. Propeller mounting and tips. 

2. All external bolts and nuts. 



CHAPTER LVIII 

Lubricating Oils, Tests, Etc. 

Lubricating oils are classified as follows: (1) Mineral oils, 
(2) fixed oils, (3) blown or thickened oils, (4) rosin oils, 
(5) lubricants containing soap, greases, (6) deflocoulated 
graphite — Aquadag and Oildag. 

Mineral Oils are extensively manufactured from crude 
petroleum and shale oil. They contain a great variety 
of hydrocarbons, the lightest of which compose crude 
naptha from which gasoline, petrol and motor spirit and 
similar products are obtained. These liquids are devoid of 
lubricating properties. They are highly inflammable and 
are used for driving motors, dry cleaning, solvents, etc. 
Hydrocarbons of higher boiling point and specific gravity 
which are too fluid and volatile for use as lubricants are 
utilized to manufacture kerosene, petroleum, paraffin oil, 
etc. The heaviest and least volatile hydrocarbons are alone 
used in the manufacture of lubricating oils, paraffin wax and 
vaseline. The refiners separate the various products from the 
crude oil and purify them for use, this being done by dis- 
tillation and chemical treatment. The value of distillation 
depends upon the fact that the different constituents of the 
crude oil boil and volatilize at different temperatures, the 
naptha coming off first, illuminating oils second, then inter- 
mediate oils from which illuminating oils are made by same 
being destructively distilled, leaving the heaviest hydro- 
carbons in the still; by separate fractional distillation, the 
naptha is subsequently split up into gasoline, etc., and the 
remainder into lubricating oils of various grades, paraffin 
wax, and asphalt or coke. 

420 



LUBRICATING OILS, TESTS, ETC. 421 

Fixed Oils. Fixed oils, so-called because they are not 
volatile without decomposition, are found ready formed in 
certain tissues of animals and plants. Fixed oils include 
such oils as castor, rape, lard, cottonseed, whale, etc. 

Blown or Thickened Oils. The blown oils used for lubrica- 
tion are usually rape or cottonseed oils, which have been 
artificially thickened by forcing a current of air through 
heated oil. 

Rosin Oils. Rosin oil is obtained from the destructive 
distillation of common rosin. 

Lubricants Containing Soap, Grease. Such lubricants are 
artificially thickened by dissolving soap in minerals — used 
for cup and engine greases. 

Deflocculated Graphite. Aquadag and Oildag. A paste of 
deflocculated graphite and water, known as " Aquadag" is 
added to lubricating oil in a mixing machine, the water 
being thrown out leaving the graphite in a paste form. 
Oildag added to mineral oil increases the lubricating value 
of oil where solid friction exists. 

TESTS FOR LUBRICATING OILS 

1. Gravity, Baume, at 60° F. 

2. Flash, Cleveland open cup. 

3. Fire, Cleveland open cup. 

4. Viscosity, Saybolt Universal viscosimeter, at 100°, 150°, 
and 212° F. 

5. Pour test as described below. 

6. Acid. 

Specific Gravity 

Apparatus. Set of hydrometers. 

Method. The hydrometers as supplied in the field testing 
outfit are marked with the specific gravity direct. 



422 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Since all specific gravities are comparable at 60° F., the 
results should be reported in degrees Baume at 60° F. 

Flash and Fire Test 

The flash point is the degree of temperature at which 
ignitable volatile vapors are given off by the oil,, producing a 
flash when brought in contact with a small flame. The fire 
test is a continuation of the flash test until the oil per- 
manently ignites. 

Apparatus. The apparatus for the flash and fire test 
consists of the following: 

a. Cleveland open-cup tester, as recommended by the 
Bureau of Mines. 

b. Alcohol lamp or gas burner. 

c. Thermometer with range to 600° F. ; corrected for bulb 
immersion. 

d. Wax tapers or gas jet. 

Method. This test shall be made in the Cleveland open- 
cup tester, the apparatus being used without any bath or 
outer cup surrounding the oil cup. The oil cup should have 
two marks on the inside — the first, J inch below the top, and 
the second f inch below, the first to be used when testing 
oils with a flash point below 425° F., and the second when 
testing oils with a flash point at or above 425° F. The 
clean oil cup should be inserted into the tripod ring, which 
must be level, and the cup filled to the proper mark with 
the oil to be tested. Care should be exercised not to spill 
any oil on the sides or top of the cup, and if this accident 
should happen, all such oil must be carefully removed. 

A "bulb immersion" thermometer should then be inserted 
into the oil, and suspended from a suitable support. The 
bulb of the thermometer should be f to f inch in length. 
During the test the bulb must be fully covered by the oil 



LUBRICATING OILS, TESTS, ETC. 423 

and the bottom of the thermometer must not be less than 
J inch from the bottom of the cup. The thermometer must 
be suspended in the oil midway between the center and inside 
edge of the cup. The alcohol or gas burner is then placed 
under the oil cup so as to heat it uniformly. The oil may 
be heated rapidly at first, but the rate of heating should be 
8° to 10° F. (5° C.) per minute during the last 80° of heating 
prior to attaining the flash point. As the flash point is 
approached, a test is made for every 5° F. rise in temperature 
(on the readings which are multiples of 5) by slowly passing 
a small bead-like test flame, or lighted wax taper, not 
exceeding J inch in length, across the center of the cup J 
inch above the surface of the oil, the movement occupying 
one second. 

The temperature when a flame first jumps from the test 
flame to the oil is called the flash point of the oil. The test 
must be made where the cup is free from draft and must be 
made in a subdued light. 

After the flash point has been obtained, the same method 
of testing shall be continued until the oil takes fire and 
continues to burn. The temperature at which the oil con- 
tinues to burn is the fire point of the oil. 

To extinguish the fire after the fire point has been taken, 
remove the thermometer and alcohol lamp and then place 
the lid over the burning oil. 

Viscosity Test 

Apparatus, a. Saybolt standard universal viscosimeter. 

b. Stop watch. 

c. Thermometers. Range 270° F. 

Method. Viscosity shall be determined by means of the 
Saybolt standard universal viscosimeter, as described in the 
Proceedings of the American Society for Testing Materials, 
Vol. XIX, Part 1, 1919. 



424 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

Viscosity shall be determined at 100° F. (37.8° C.), 130° F. 
(54.4° C.) or 210° F. (98.9° C.). The bath shall be held 
constant within 0.25° F. (0.14° C.) at such a temperature 
as will maintain the desired temperature in the standard oil 
tube. For viscosity determinations at 100° and 130° F., 
oil or water may be used as the bath liquid. For viscosity 
determinations at 210° F., oil shall be used as the bath 
liquid. The oil for the bath liquid should be a pale engine 
oil of at least 350° F. flash point (open cup). Viscosity 
determinations shall be made in a room free from drafts 
and from rapid changes in temperature. All oil introduced 
into the standard oil tube, either for cleaning or for test, 
shall first be passed through the strainer. 

The outer bath is filled with a paraffin engine oil with a 
flash of about 350° to 400° F., and the temperature is adjusted 
by letting cold water flow through the U-tube or by heating, 
as may be necessary. The tube, which incloses a small jet, 
is closed by a cork, which is inserted just far enough to be 
air-tight and not nearly far enough to touch the jet. The oil, 
previously strained into a tin cup and heated to about the 
required temperature, is poured into the tube until it over- 
flows and fills the cup above the level of the upper end. It 
is then stirred with a thermometer until the temperature is 
exactly adjusted. The thermometer is withdrawn and the 
surplus oil is removed from the gallery by a pipette. The 
cork is then withdrawn and the number of seconds occupied 
in filling the flask to the 60 cc. mark is noted by a stop watch 
and recorded as the viscosity in seconds. 

Pour Test 

The pour test indicates the temperature at which a sample 
of oil in a cylindrical container of specified diameter and 
length will just flow under specified conditions. 

Apparatus. The apparatus for the pour test consists of 
the following: 



LUBEICATING OILS, TESTS, ETC. 425 

a. Glass jar, approximately If inches inside diameter and 
4 to 5 inches high, provided with a tightly fitting cork. 

b. Mercury thermometer, fitted securely in the cork so 
that the shaft will be held centrally in the jar with the tip 
of the bulb § inch from the bottom. The thermometer 
specially made for this test has a bulb J to f inch long. 

Method. Place the oil in the jar to a depth of about lj 
inches or to a sufficient depth to reach \ inch above the bulb 
of the thermometer; fit the cork tightly into the jar and 
place the jar in a freezing mixture. At each drop in tem- 
perature of 5° F. remove the jar from the freezing mixture 
and tilt it just enough to make the oil flow. The pour test 
of the oil shall be taken as 5° higher than the reading of the 
thermometer when the oil has cooled so that it will not flow 
when the jar is tipped to a horizontal position. 

The rate of cooling should be such that the pour test will 
be completed in about one-half hour. 

The materials used in the freezing mixture vary with 
the temperature required to cause the lubricant to solidify. 
Cracked ice will be sufficient for a temperature above 35° F. 
For temperatures between 15° and 35° F. a mixture consisting 
of 1 volume of salt and 20 volumes of ice may be used. The 
salt for this purpose should be very dry and fine enough to 
pass a 20-mesh screen. From 15° to —5° F., ice and salt in 
the proportions of 1 to 2 are suitable. From 0° to —25° F. a 
mixture of ice and calcium chloride is used. For tempera- 
tures lower than — 5° a mixture of solid carbon dioxide and 
acetone is more convenient and will produce temperatures of 
-70° F. or less. 

The carbon dioxide-acetone mixture may be made as 
follows: Place a sufficient amount of dry acetone in a 
covered copper or nickel beaker; place the beaker in an ice- 
salt mixture, and when the acetone reaches 10° F. or less, 
add solid carbon dioxide gradually until the desired tem- 
perature is reached. 



426 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

To obtain the solid carbon dioxide, invert an ordinary 
liquefied carbon-dioxide cylinder, open the valve carefully, 
and let the gas flow into a chamois-skin bag. Rapid evapora- 
tion will cause the carbon dioxide to solidify. 

Acidity Test 

Acidity in oils is generally due to a partial decomposition 
of the oil with liberation of fatty acids. These latter act as 
corrosive agents, attacking the metal of machinery, forming 
"metallic soaps," and producing gumming and thickening of 
the lubricant. 

Properly refined mineral oils are free from acidity, but 
nearly all animal and vegetable oils possess it more or less. 

Lubricating oils should be neutral and show no trace of 
acids. 

Apparatus. Litmus paper. 

Method. Rub a small quantity of oil on a piece of polished 
brass or copper. The metal must not turn green after 
standing for twenty-four hours. 

Another method to determine the acidity of an oil is to 
wash a small quantity of the oil with distilled water, then 
drain off the water and place a piece of litmus paper in the 
water. If the litmus paper turns red, acid is present; if the 
paper turns blue, alkali is present; if there is no change, the 
oil is neutral. The paper should remain unchanged. 



CHAPTER LIX 

Oil Reclamation 

Oil taken from the crankcase of internal combustion 
engines usually contains considerable free carbon in suspen- 
sion, dirt, grit and possibly some water. 

Generally, too, in the case of gasoline or kerosene engines, 
some of the heavy ends of the gasoline or kerosene have 
leaked past the piston rings into the oil, thus contaminating 
it and reducing its viscosity to such an extent as to make it 
unfit for further use in engines. 

Laboratory and running tests made by the United States 
Bureau of Standards have demonstrated beyond a doubt that 
oil does not wear out. The oil does accumulate the impur- 
ities mentioned above, which render it unfit for long con- 
tinued use ; but if these impurities are removed entirely, and 
the body of the oil brought back to its original viscosity, 
the reclaimed oil can be used again in the engines from which 
it was taken with exactly the same satisfactory results as if 
new oil was used. 

As a matter of fact these tests have shown that reclaimed 
oil deposits less carbon in an engine than the same oil when 
new. Certain constituents which tend to form carbon 
deposits are thrown out of the oil during its use in an engine. 
The process of reclaiming this oil really refines it, removing 
these carbon forming elements. 

The Oil Reclaiming Plant at the Naval Air Station, 
Pensacola, Florida, is equipped with three Richardson 
Phoenix purifiers with a daily capacity of 375 gallons. With 
intermittent operation, the cost of reclamation is estimated 
at ten cents per gallon, which would be materially reduced 

427 



428 AIRPLANES, AIRSHIPS, AIRCRAFT ENGINES 

by a capacity production. Dirty oil is dumped into a vat 
on the unloading platform outside the plant, from whence it 
flows by gravity to the dirty oil tanks inside the building. 
From these tanks it is delivered by service oil pumps to the 
purifiers. Here by the introduction of live steam the oil is 
agitated and volatiles driven off. 

If the oil to be reclaimed contains more than ten per cent 
gasoline, this can be profitably reclaimed by condensing the 
fumes driven off during agitation of the oil. The length of 
time necessary to agitate the oil with steam depends entirely 
upon the brand of oil, the amount of dirt and volume of 
gasoline or kerosene in it 

The duration of agitation must be determined by actual 
experiment. Samples may be drawn off at any time and 
subjected to a flash test. 

When the flash point of the sample has been brought as 
high as the flash point of the same oil when new, it is evident 
that the steaming has been carried on long enough to drive 
off the gasoline and kerosene ends. 

The average maximum steaming time is one hour with 
steam at 30 pounds pressure. 

After steam agitation has been completed, from J to J of 
a pound of soda ash or sal soda for each gallon to be treated, 
should be thoroughly dissolved in sufficient water to obtain 
a saturated solution and the solution mixed with the oil. 

The function of the soda is to coagulate the carbon and 
other suspended impurities in the oil. 

It is not necessary to add water to used motor oils when 
being purified. Sufficient water is naturally added by steam 
condensation during agitation and with the soda solution. 

After introducing the soda solution, the mixture is again 
agitated for a period of about fifteen minutes to assure a 
thorough intimate mixture of the soda solution with the oil. 

The oil is now allowed to settle. A period of ten hours is 
usually sufficient. 



OIL EECLAMATION 429 

After settling process has been completed the mixture is 
divided into three layers. At the bottom is a layer of water. 
Above this is a layer of "sludge." On top is the clean oil. 

The oil is removed from the purifier by displacing it with 
water. It should be drawn off at a temperature of not less 
than 120° F. Piping leading to storage tank is thoroughly 
flushed and the clean oil drawn off into the clean oil storage 
tank, ready for issue. 



INDEX 

Page 

Aerostatics, Formulae For 301 

Air, Weight of 256 

Aircraft Don'ts, Heavier-Than-Air 178 

Don'ts, Lighter-Than-Air 310 

Heavier-Than-Air, In Storage — Care and Preservation 

Of 176 

Overhaul and Alignment Of 164 

Wires— Types, Strengths, Etc 94 

Airship — Advantage Over Airplane 271 

How Car Is Connected 247 

How Inflated From Flasks 244 

Inspection Before Flight 254 

Inspection Of 235 

Life of Fabric 248 

Method of Preventing Tail Droop 304 

Mooring 305 

Placing in Storage 253 

Precautions in Inflating 273 

Things To Remember 313 

Air Speed Meter — Functions, Troubles, Etc 185 

Altimeter-Functions, Troubles, Etc 192 

Aluminum — Its Alloys, Table of Strengths 155 

Paint— Number Of Coats To Be Applied 137 

Powdered— Quantity To Be Used 240 

Powdered — Use On A Balloon 240 

Appendix — Description, Use, Etc 256 

Ballast— Best To Be Used 257 

Ballonets— Their Uses 251 

Balloon— Brief History Of 223 

Dilatable Or Expanding Gore 298 

Factor Of Safety Of ; 256 

Free Equipment Of 291 

Folding For Storage 252 

Inspection Before Flight 254 

Landing Of 293 

Night Flying 295 

431 



432 INDEX 

Balloon — How Inflated From Flasks 244 

Inspection Of '. 235 

Kite — Communication With 261 

Difference Between "M" and "IT' Types 274 

Inspection Before Flight 254 

Instruments Carried In 277 

Placing In Storage 252 

Stabilizer Rigging 275 

Life Of Fabric 248 

Smoking In Vicinity Of 263 

Term "Lift" Defined 267 

Ballooning — Fundamentals Of Operation 286 

Bar, Supension 275 

Barograph, Recording 197 

Battens— Their Uses 249 

Battery, Storage — Types, Description, Upkeep, Etc 344 

Bolts, Hexagon Head 120 

Brazing 112 

Brazing Material — Composition Of 125 

Cable, Kite Balloon,— Strength Of 277 

Carburetor, Float Feed 370 

Zenith— Description Of 371 

Zenith — 'Setting Of Jets and Compensators 373 

Checking Alignment Of Seaplanes On Beach. 172 

Clevis Pins 107 

Comalong Or Cable Grip, And Its Use 231 

Compass, Aero — Description, Compensation, Etc 206 

Coupling, Quick Attachment 275 

Definitions For Various Other Terms Used In Aircraft 46 

Dope, Delta— Its Use 240 

.—Method Of Applying To Lighter-Than-Air Craft 240 

Dopes And Solvents 145 

Dry Kilning Aircraft Material 85 

Duralumin — Properties And Use Of 158 

Electric Generator Or Dynamo — How Generator Armatures Are 

Wound 341 

Electric Generator Troubles And Their Causes 342 

Electrical Current Production In Aircraft Engines 331 

Ignition System 329 



INDEX 433 

Electricity — Brush Discharge 266 

Electric Charge At High Speed 267 

Fundamental Units 338 

Static — How Induced 258 

Enamel, Black 128 

Enamelling And Painting Metal Parts 126 

Engine, Aircraft — Construction Of 332 

Cooling System 336 

Description And Classes 322 

Hispano-Suiza — Description Of 411 

Hispano-Suiza — How To Time Same 415 

Hispano-Suiza — Lubrication System 413 

Internal Combustion 320 

Liberty — History And Description Of 388 

Liberty— How To Time Same 403 

Liberty— Order Of Tear Down 394 

Lubrication Of 334 

Preliminary Units And Definitions 316 

Reliability Of 326 

Rotary 324 

Routine Inspection By Aircraft Engine 

Mechanic 417 

Troubles 381 

Troubles, Auxiliary, That Cause Stoppage 383 

Troubles, Structural 385 

Engines, Aircraft — Used By The Navy — How Classified 325 

Top Overhaul After Storage 416 

Fabric, Balloon— Its Manufacture, Number Of Plies, Etc' 250 

Permeability Of 261 

Cotton, Rubberized 267 

Doping System 137 

Precautions When Covering A New Or Recovering An 

Old Wing 138 

Repairs To Large Or Small Tears 137 

Fabrics — Characteristics Of, Etc 129 

Their Application 129 

Fittings — Manufacture Of 108 

Flask, Hydrogen — Capacity And Weight 264 

How Charged, Number Of Pounds Pressure. 265 
How Painted 265 



434 INDEX 

Flask, Hydrogen— Material Made Of, Etc 263 

Precautions When Charging 264 

Test Of, For Strength 265 

Forces Acting Upon Plane 266 

Fuselage Construction 62 

Gas— Diffusion Of 228 

Of That Would Warrant Re-doping 261 

Helium 270 

Hydrogen— Weight Of 264 

Testing Purity Of 229 

Transportation Of 233 

Gases— Kinds Of 224 

Their Manufacture 225 

Gasoline Carburetion And Carburetors 357 

Mixture And Proportion 328 

— Special Class For Aeroplane Purposes, Specifications, 

Inspection 359 

Gauge, Pressure — Description, Etc 212 

Temperature — Description, Calibration, Etc 211 

Glues And Their Uses 143 

Harness, Mooring 268 

Heat Treatment Of Metals 109 

Ignition System, Liberty Engine from Source to Plug 350 

Incidence, Angle of 59 

Indicator, Gyro Turn 216 

Side Slip— Description, Etc. 213 

Induction Coils and Distributors 349 

Insignia, Airship 151 

Free Balloons 153 

Heavier-than-Air Craft 149 

How Painted 148 

Kite Balloons. 153 

Inspection of Seaplanes after Flight 173 

Junction Piece — Its Uses 269 

Knots— Kinds of 270 



INDEX 435 

Leak Detector, Hydrogen— Description, Etc 218 

Level, Fore and Aft— Description, Etc ' 215 

Magnetism, Magneto, Etc 339 

Magneto, Dixie 355 

Magnetos — Description of 354 

Dixie — How to Sychronize 356 

Manifolds— Types of, Etc ! .- 265 

Manometer — Description of, Etc 220 

Gauge — What It Designates 250 

Metal Impurities 118 

Tested for Hardness 119 

Meter, Edwards Effusion 230 

Navy Terminal Splice— How Made 96 

Nomenclature for Aeronautics, Alphabetically 11 "to 52 

Nuts, Aircraft, Hexagon 120 

Oils, Lubricating — Manufacture and Test 420 

Used — Reclamation of 427 

Paints— Kinds of 147 

Parachutes — Folding of Same 271 

In Storage — How Cared for 177 

Patch, Finger— Its Use, Etc 247 

Pickets— What Made of and Uses 270 

Pipes — Their Marking 154 

Pontoon — Construction of 141 

Potash Bath — Composition of 122 

Propeller Manufacture 88 

Proving Load Table, Control Wire 99 

19 Strand Wire 100 

Rip Panel — Installation of 238 

Its Use 237 

Rope, Drag— How to Determine Length of 256 

Rigging— Its Use 249 

Ropes, Furling 269 

Hemp — Insulators or Not 267 

Rudder, Airship — Inspection of 258 

Rust Proofing 122 



436 INDEX 

Sand Bag Filled— Weight of 262 

How Made. . 262 

Blasting and Pickling 121 

Weight of 262 

Seamless Copper Tubes 124 

Seams in Balloons — How Secured Together 251 

Shackles 107 

Statoscope, Liquid Type — Description, Etc 221 

Steel And Copper Tubes 124 

Suspension, Mid — Its Use 270 

Rear 270 

Tachometer — Description, Troubles, Etc 201 

Terminals, How Made in 19 Strand Galvanized Wire 10G 

Rigid, for Stream Line or Swaged Wire 103 

Tests— Kinds And Definitions of 116 

Tube, Nurse — Description and Use 275 

Turnbuckles 105 

Table of Strengths, Etc 106 

Types of Planes 60 

Valve, Check — How Made and Where Used in a Kite Balloon.. 276 

Gammeter — Its Use, Description of, Etc 241 

Inflation — Description and Use of 277 

Valves— Automatic Operation of 262 

Control Wires, How Connected 273 

Precautions to be Taken When Valving 246 

Washers— Kinds, Etc 120 

Water— Weight of 262 

Winch, Kite Balloon— Complete Instructions for Operating 279 

Upkeep of 259 

Wing — Beam Splices 94 

Heaviness, Right or Left — How to Correct 174 

Wood — Material Used in Construction of Flying Boats 139 

Protective Coatings 91 

Woods — Specifications for 76 

Used in the Construction of Aircraft 67 



HARTSHORN STREAMLINE WIRES 

Assembled with Hartshorn Universal Strap Ends make 
the Ideal Aeroplane Tie Rods— diminished wind resist- 
ance insuring greater speed. 

This fact was proved in the speed test for the Pulitzer 
Trophy. Four of the first five ships were equipped with 
Hartshorn Streamline Tie Rods. 

Write for circular A-l [describing our Wires and Strap 
End Fittings. 



STEWART HARTSHORN CO 

250 FIFTH AVENUE, NEW YORK 



BRASS, BRONZE, NICKEL SILVER 

TO GOVERNMENT SPECIFICATIONS 

Sheets, Plates, Rods, Wire, Cups, Circles 
Seamless Brass and Copper Tubing 

Extruded Rods, Machine and Cap Screws, Buttons, Brass 
Castings and Forgings, Scovill Special Spring Bronze, 
Naval Brass, Small parts to order in large quantities. 
Stampings. Screw Machine Products. Misc. 

TECHNICAL CONTROL IN OUR MILLS AND 
FACTORIES WILL INSURE MATERIAL WHICH 
IS UNIFORMLY CORRECT. 

SCOVILL MANUFACTURING COMPANY 

ESTABLISHED 1602 

WATERBURY, CONNECTICUT 

NEW YORK, BOSTON, CHICAGO, DETROIT, PHILADELPHIA, 
ROCHESTER, CLEVELAND. 



AIRPLANES 
AIRPLANE INSTRUMENTS 



Design 



Manufacture 



Development 



THE LAWRENCE SPERRY AIRCRAFT CO., Inc. 

Farmingdale Long Island, N. Y. 



ENGINEERING 
DESIGNING 



PARTS 
SUPPLIES 



VALENTINE GEPHART, INC, 




AIRCRAFT BUILDERS 
KANSAS CITY, MO. 

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PIONEER. INSTRUMENTS 

STANDARD AIRCRAFT EQUIPMENT 



CONTRACTORS 
TO 

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PIONEER INSTRUMENT COMPANY 
136 Havemeyer Street Brooklyn N Y 



JOHNSON AIRPLANE AND 
SUPPLY COMPANY 

Dayton, Ohio 

Airplanes, airplane parts and acces- 
sories of every description. New and 
used motors of all makes. 

A completely equipped flying field 
where you will receive prompt and cour- 
teous service. 

Write for prices on remodeling your 
plane to carry any motor desired. 

Price lists mailed on request. 




FAITH 



The Dayton Wright 
Company believes in 
aviation— foresees with 
calm assurance the 
service which aircraft 
will render to Com- 
merce and Industry. 



It is pleased to consider that the 
opportunity to share in the develop- 
ment and in the accomplishment of its 
expectations of the aircraft industry is 
both a privilege and a trust. 

Permit us to study your transpor- 
tation problems. Probably you are 
one who may profit by the use of the 
aircraft. 

Dayton Wright Co. 

Dayton, Ohio, U. S. A. 





"The birthplace of the airplane " 



'/- 



■% 



